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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 09, 2018
Document Information [Line Items]
Entity Registrant Name	SL GREEN REALTY CORP
Entity Central Index Key	0001040971
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		88,422,771
SL Green Operating Partnership
Document Information [Line Items]
Entity Registrant Name	SL GREEN OPERATING PARTNERSHIP, LP.
Entity Central Index Key	0001492869
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		1,468,438

Consolidated Balance Sheets - USD ($)
$ in Thousands

Mar. 31, 2018

Dec. 31, 2017

Commercial real estate properties, at cost:

Land and land interests

$ 2,098,406

$ 2,357,051

Building and improvements

5,206,982

6,351,012

Building leasehold and improvements

1,420,346

1,450,614

Properties under capital lease

47,445

Total commercial real estate properties, at cost

8,773,179

10,206,122

Less: accumulated depreciation

(1,944,629)

(2,300,116)

Total commercial real estate properties, net

6,828,550

7,906,006

Assets held for sale

67,819

338,354

Cash and cash equivalents

288,808

127,888

Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents

378,265

Restricted cash

89,457

122,138

Investments in marketable securities

28,252

28,579

Tenant and other receivables, net of allowance of $18,363 and $18,637 in 2018 and 2017, respectively

49,552

57,644

Related party receivables

31,305

23,039

Deferred rents receivable, net of allowance of $16,897and $17,207 in 2018 and 2017, respectively

320,547

365,337

Debt and preferred equity investments, net of discounts and deferred origination fees of $24,998 and $25,507 in 2018 and 2017, respectively

2,085,871

2,114,041

Investments in unconsolidated joint ventures

3,034,596

2,362,989

Deferred costs, net

195,557

226,201

Other assets

360,556

310,688

Total assets

^[1]

13,380,870

13,982,904

Liabilities

Mortgages and other loans payable, net

2,433,994

2,837,282

Revolving credit facility, net

30,336

Unsecured term loan, net

1,491,922

1,491,575

Unsecured notes, net

1,396,320

1,395,939

Accrued interest payable

36,808

38,142

Other liabilities

103,654

188,005

Accounts payable and accrued expenses

131,797

137,142

Deferred revenue

177,896

208,119

Capital lease obligations

43,029

42,843

Deferred land leases payable

3,403

3,239

Dividend and distributions payable

82,337

85,138

Security deposits

64,647

67,927

4,074

Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities

100,000

Total liabilities

^[1]

6,065,849

6,629,761

Commitments and contingencies

Noncontrolling interests in Operating Partnership

475,807

461,954

Preferred units

301,585

301,735

Equity

Series I Preferred Stock, $0.01 par value, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2018 and December 31, 2017

221,932

Common stock, $0.01 par value, 160,000 shares authorized and 90,190 and 93,858 issued and outstanding at March 31, 2018 and December 31, 2017, respectively (including 1,055 shares held in treasury at March 31, 2018 and December 31, 2017)

902

939

Additional paid-in-capital

4,776,594

4,968,338

Treasury stock at cost

(124,049)

Accumulated other comprehensive income

28,573

18,604

Retained earnings

1,583,833

1,139,329

Total SL Green stockholders' equity

6,487,785

6,225,093

Noncontrolling interests in other partnerships

49,844

364,361

Total equity

6,537,629

6,589,454

SL Green stockholders equity:

Total liabilities and equity/capital

13,380,870

13,982,904

SL Green Operating Partnership

Commercial real estate properties, at cost:

Land and land interests

2,098,406

2,357,051

Building and improvements

5,206,982

6,351,012

Building leasehold and improvements

1,420,346

1,450,614

Properties under capital lease

47,445

Total commercial real estate properties, at cost

8,773,179

10,206,122

Less: accumulated depreciation

(1,944,629)

(2,300,116)

Total commercial real estate properties, net

6,828,550

7,906,006

Assets held for sale

67,819

338,354

Cash and cash equivalents

288,808

127,888

Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents

378,265

250,026

Restricted cash

89,457

122,138

Investments in marketable securities

28,252

28,579

Tenant and other receivables, net of allowance of $18,363 and $18,637 in 2018 and 2017, respectively

49,552

57,644

Related party receivables

31,305

23,039

Deferred rents receivable, net of allowance of $16,897and $17,207 in 2018 and 2017, respectively

320,547

365,337

Debt and preferred equity investments, net of discounts and deferred origination fees of $24,998 and $25,507 in 2018 and 2017, respectively

2,085,871

2,114,041

Investments in unconsolidated joint ventures

3,034,596

2,362,989

Deferred costs, net

195,557

226,201

Other assets

360,556

310,688

Total assets

^[2]

13,380,870

13,982,904

Liabilities

Mortgages and other loans payable, net

2,433,994

2,837,282

Revolving credit facility, net

30,336

Unsecured term loan, net

1,491,922

1,491,575

Unsecured notes, net

1,396,320

1,395,939

Accrued interest payable

36,808

38,142

Other liabilities

103,654

188,005

Accounts payable and accrued expenses

131,797

137,142

Deferred revenue

177,896

208,119

Capital lease obligations

43,029

42,843

Deferred land leases payable

3,403

3,239

Dividend and distributions payable

82,337

85,138

Security deposits

64,647

67,927

4,074

Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities

100,000

Total liabilities

^[2]

6,065,849

6,629,761

Commitments and contingencies

Noncontrolling interests in Operating Partnership

475,807

461,954

Limited partner interests in SLGOP (4,715 and 4,453 limited partner common units outstanding at March 31, 2018 and December 31, 2017, respectively)

475,807

461,954

Preferred units

301,585

301,735

Equity

Accumulated other comprehensive income

28,573

18,604

SL Green stockholders equity:

Series I Preferred Units, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2018 and December 31, 2017

221,932

SL Green partners' capital (939 and 973 general partner common units and 88,196 and 91,831 limited partner common units outstanding at March 31, 2018 and December 31, 2017, respectively)

6,237,280

5,984,557

Total SLGOP partners' capital

6,487,785

6,225,093

Noncontrolling interests in other partnerships

49,844

364,361

Total capital

6,537,629

6,589,454

Total liabilities and equity/capital

$ 13,380,870

$ 13,982,904

[1]

The Company's consolidated balance sheets include assets and liabilities of consolidated variable interest entities ("VIEs"). See Note 2. The consolidated balance sheets include the following amounts related to our consolidated VIEs, excluding the Operating Partnership: $174.8 million and $398.0 million of land, $0.3 billion and $1.4 billion of building and improvements, $2.0 million and $2.0 million of building and leasehold improvements, $47.4 million and $47.4 million of properties under capital lease, $29.8 million and $330.9 million of accumulated depreciation, $706.0 million and $221.0 million of other assets included in other line items, $134.4 million and $628.9 million of real estate debt, net, $0.4 million and $2.5 million of accrued interest payable, $43.0 million and $42.8 million of capital lease obligations, and $17.7 million and $56.8 million of other liabilities included in other line items as of September 30, 2017 and December 31, 2016, respectively.

[2]

The Operating Partnership's consolidated balance sheets include assets and liabilities of consolidated variable interest entities ("VIEs"). See Note 2. The consolidated balance sheets include the following amounts related to our consolidated VIEs, excluding the Operating Partnership: $174.8 million and $398.0 million of land, $0.3 billion and $1.4 billion of building and improvements, $2.0 million and $2.0 million of building and leasehold improvements, $47.4 million and $47.4 million of properties under capital lease, $29.8 million and $330.9 million of accumulated depreciation, $706.0 million and $221.0 million of other assets included in other line items, $134.4 million and $628.9 million of real estate debt, net, $0.4 million and $2.5 million of accrued interest payable, $43.0 million and $42.8 million of capital lease obligations, and $17.7 million and $56.8 million of other liabilities included in other line items as of September 30, 2017 and December 31, 2016, respectively.

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Tenant and other receivables, allowance	$ 18,363	$ 18,637
Deferred rents receivable, allowance	16,897	17,207
Debt and preferred equity investments, discount and deferred origination fees	$ 24,998	$ 25,507
Preferred stock, par value (in dollars per share)	$ 0.01
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	160,000,000
Common stock, shares issued (in shares)	90,190,000	93,858,000
Common stock, shares outstanding (in shares)	90,190,000	93,858,000
Treasury stock, shares (in shares)	1,055,000	1,055,000
Land and land interests	$ 2,098,406	$ 2,357,051
Building and improvements	5,206,982	6,351,012
Building leasehold and improvements	1,420,346	1,450,614
Properties under capital lease	47,445	47,445
Accumulated depreciation	1,944,629	2,300,116
Other assets	360,556	310,688
Mortgages and other loans payable, net	2,433,994	2,837,282
Accrued interest payable	36,808	38,142
Capital lease obligations	43,029	42,843
Other liabilities	$ 103,654	$ 188,005
Series I Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred stock, shares issued (in shares)	9,200,000	9,200,000
Preferred stock, shares outstanding (in shares)	9,200,000	9,200,000
Consolidated VIEs
Land and land interests	$ 174,800	$ 398,000
Building and improvements	300,000	1,400,000
Building leasehold and improvements	2,000	2,000
Properties under capital lease	47,400	47,400
Accumulated depreciation	29,800	330,900
Other assets	706,000	221,000
Mortgages and other loans payable, net	134,400	628,900
Accrued interest payable	400	2,500
Capital lease obligations	43,000	42,800
Other liabilities	17,700	56,800
SL Green Operating Partnership
Tenant and other receivables, allowance	18,363	18,637
Deferred rents receivable, allowance	16,897	17,207
Debt and preferred equity investments, discount and deferred origination fees	$ 24,998	$ 25,507
Limited partner interests in Operating Partnership, limited partner common units outstanding (shares)	4,715,000	4,453,000
SL Green partner's capital, general partner common units outstanding (shares)	939,000	973,000
SL Green partners' capital, limited partner common units outstanding (shares)	88,196,000	91,831,000
Land and land interests	$ 2,098,406	$ 2,357,051
Building and improvements	5,206,982	6,351,012
Building leasehold and improvements	1,420,346	1,450,614
Properties under capital lease	47,445	47,445
Accumulated depreciation	1,944,629	2,300,116
Other assets	360,556	310,688
Mortgages and other loans payable, net	2,433,994	2,837,282
Accrued interest payable	36,808	38,142
Capital lease obligations	43,029	42,843
Other liabilities	$ 103,654	$ 188,005
SL Green Operating Partnership \| Series I Preferred Stock
Preferred units, liquidation preference (in dollars per share)	$ 25.00	$ 25.00
Preferred units, shares issued (in shares)	9,200,000	9,200,000
Preferred units, shares outstanding (in shares)	9,200,000	9,200,000
SL Green Operating Partnership \| Consolidated VIEs
Land and land interests	$ 174,800	$ 398,000
Building and improvements	300,000	1,400,000
Building leasehold and improvements	2,000	2,000
Properties under capital lease	47,400	47,400
Accumulated depreciation	29,800	330,900
Other assets	706,000	221,000
Mortgages and other loans payable, net	134,400	628,900
Accrued interest payable	400	2,500
Capital lease obligations	43,000	42,800
Other liabilities	$ 17,700	$ 56,800

Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Rental revenue, net	$ 215,369	$ 281,329
Escalation and reimbursement	26,399	44,192
Investment income	45,290	40,299
Other income	14,637	11,561
Total revenues	301,695	377,381
Expenses
Operating expenses, including related party expenses of $3,834 in 2018 and $4,173 in 2017.	59,782	74,506
Real estate taxes	45,661	61,068
Ground rent	8,308	8,308
Interest expense, net of interest income	47,916	65,622
Amortization of deferred financing costs	3,537	4,761
Depreciation and amortization	69,388	94,134
Transaction related costs	162	133
Marketing, general and administrative	23,528	24,143
Total expenses	258,282	332,675
Income before equity in net income from unconsolidated joint ventures, equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities	43,413	44,706
Equity in net income from unconsolidated joint ventures	4,036	6,614
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440)	2,047
Purchase price and other fair value adjustments	49,293	0
Gain on sale of real estate, net	23,521	567
Depreciable real estate reserves	0	(56,272)
Gain on sale of investment in marketable securities	0	3,262
Net income	113,823	924
Net (income) loss attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(5,272)	(476)
Noncontrolling interests in other partnerships	(198)	17,491
Preferred units distributions	(2,849)	(2,850)
Net income (loss) attributable to SL Green/SLGOP	105,504	15,089
Perpetual preferred stock dividends	(3,738)	(3,738)
Amounts attributable to SL Green common stockholders:
Income before depreciable real estate reserves and gains on sale and fair value adjustments	38,657	62,660
Purchase price and other fair value adjustments	46,868	0
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,123)	1,957
Gain on sale of real estate, net	22,364	542
Depreciable real estate reserves	0	(53,808)
Net income attributable to SL Green common stockholders	$ 101,766	$ 11,351
Basic earnings per share:
Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share)	$ 0.43	$ 0.62
Purchase price and other fair value adjustments (in dollars per share)	0.52	0.00
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share)	(0.07)	0.02
Gain on sale of real estate, net (in dollars per share)	0.24	0.01
Depreciable real estate reserves (in dollars per share)	0.00	(0.54)
Net income attributable to SL Green common stockholders (usd per share)	1.12	0.11
Diluted earnings per share:
Purchase price and other fair value adjustments (in dollars per share)	0.52	0.00
Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share)	0.43	0.62
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share)	(0.07)	0.02
Gain on sale of real estate (in dollars per share)	0.24	0.01
Depreciable real estate reserves (in dollars per share)	0.00	(0.54)
Net income attributable to SL Green common stockholders (usd per share)	1.12	0.11
Dividends per share/unit (usd per share)	$ 0.8125	$ 0.775
Basic weighted average common shares outstanding (in shares)	90,520	100,643
Diluted weighted average common shares and common share equivalents outstanding (in shares)	95,256	105,554
SL Green Operating Partnership
Revenues
Rental revenue, net	$ 215,369	$ 281,329
Escalation and reimbursement	26,399	44,192
Investment income	45,290	40,299
Other income	14,637	11,561
Total revenues	301,695	377,381
Expenses
Operating expenses, including related party expenses of $3,834 in 2018 and $4,173 in 2017.	59,782	74,506
Real estate taxes	45,661	61,068
Ground rent	8,308	8,308
Interest expense, net of interest income	47,916	65,622
Amortization of deferred financing costs	3,537	4,761
Depreciation and amortization	69,388	94,134
Transaction related costs	162	133
Marketing, general and administrative	23,528	24,143
Total expenses	258,282	332,675
Income before equity in net income from unconsolidated joint ventures, equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities	43,413	44,706
Equity in net income from unconsolidated joint ventures	4,036	6,614
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440)	2,047
Gain on sale of real estate, net	23,521	567
Depreciable real estate reserves	0	(56,272)
Gain on sale of investment in marketable securities	0	3,262
Net income	113,823	924
Net (income) loss attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(5,272)
Noncontrolling interests in other partnerships	(198)	17,491
Preferred units distributions	(2,849)	(2,850)
Net income (loss) attributable to SL Green/SLGOP	110,776	15,565
Perpetual preferred unit distributions	(3,738)	(3,738)
Net income attributable to SLGOP common unitholders	107,038	11,827
Amounts attributable to SL Green common stockholders:
Income before depreciable real estate reserves and gains on sale and fair value adjustments	40,664	65,485
Purchase price and other fair value adjustments	49,293	0
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440)	2,047
Gain on sale of real estate, net	23,521	567
Depreciable real estate reserves	$ 0	$ (56,272)
Basic earnings per share:
Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share)	$ 0.43	$ 0.62
Purchase price and other fair value adjustments (in dollars per share)	0.52	0.00
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share)	(0.07)	0.02
Gain on sale of real estate, net (in dollars per share)	0.24	0.01
Depreciable real estate reserves (in dollars per share)	0.00	(0.54)
Net income attributable to SLGOP common unitholders (usd per share)	1.12	0.11
Diluted earnings per share:
Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share)	0.43	0.62
Purchase price and other fair value adjustments (in dollars per share)	0.52	0.00
Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share)	(0.07)	0.02
Gain on sale of real estate (in dollars per share)	0.24	0.01
Depreciable real estate reserves (in dollars per share)	0.00	(0.54)
Net income attributable to SLGOP common unitholders (usd per share)	1.12	0.11
Dividends per share/unit (usd per share)	$ 0.8125	$ 0.775
Basic weighted average common shares outstanding (in shares)	95,203	105,250
Basic weighted average common units outstanding (in shares)	95,203	105,250
Diluted weighted average common units and common unit equivalents outstanding (in shares)	95,256	105,554

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses, paid to related parties	$ 3,834	$ 4,173
SL Green Operating Partnership
Operating expenses, paid to related parties	$ 3,834	$ 4,173

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net income	$ 113,823	$ 924
Other comprehensive income (loss):
Change in net unrealized gain on derivative instruments, including SL Green's/SLGOP's share of joint venture net unrealized (loss) gain on derivative instruments	10,913	(1,075)
Change in unrealized gain on marketable securities	(325)	(4,750)
Other comprehensive income (loss)	10,588	(5,825)
Comprehensive income (loss)	124,411	(4,901)
Net (income) loss attributable to noncontrolling interests and preferred units distributions	(8,319)	17,491
Net (loss) income attributable to noncontrolling interests	(198)	17,491
Other comprehensive (loss) income attributable to noncontrolling interests	(619)	199
Comprehensive income attributable to SL Green/SLGOP	115,473	12,789
SL Green Operating Partnership
Net income	113,823	924
Other comprehensive income (loss):
Change in net unrealized gain on derivative instruments, including SL Green's/SLGOP's share of joint venture net unrealized (loss) gain on derivative instruments	10,913	(1,075)
Change in unrealized gain on marketable securities	(325)	(4,750)
Other comprehensive income (loss)	10,588	(5,825)
Comprehensive income (loss)	124,411	(4,901)
Net (loss) income attributable to noncontrolling interests	(198)	17,491
Other comprehensive (loss) income attributable to noncontrolling interests	(619)	199
Comprehensive income attributable to SL Green/SLGOP	$ 123,594	$ 12,789

Consolidated Statement of Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In-Capital	Treasury Stock	Accumulated Other Comprehensive Income	Retained Earnings	Noncontrolling Interests	Series I Preferred Stock Preferred Stock
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment upon adoption of ASC 610-20 \| Accounting Standards Update 2014-09	$ 570,524						$ 570,524
Beginning Balance at Dec. 31, 2017	6,589,454		$ 939	$ 4,968,338	$ (124,049)	$ 18,604	1,139,329	$ 364,361	$ 221,932
Beginning Balance (in shares) at Dec. 31, 2017			92,803
Adjusted Balance at Dec. 31, 2017	7,159,978		$ 939	4,968,338	(124,049)	18,604	1,709,853	364,361	$ 221,932
Increase (Decrease) in Stockholders' Equity
Net income	105,702						105,504	198
Other comprehensive income	9,969					9,969
Preferred dividends	(3,738)						(3,738)
DRSPP proceeds (in shares)			1
DRSPP proceeds	42			42
Reallocation of noncontrolling interest in the Operating Partnership	3,645						3,645
Deferred compensation plan and stock awards, net (in shares)			(19)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	3,102			3,102
Repurchases of common stock (in shares)			(3,654)
Repurchases of common stock	(354,744)		$ (37)	(195,617)			(159,090)
Proceeds from stock options exercised (in shares)			4
Proceeds from stock options exercised	729			729
Contributions to consolidated joint venture interests	157							157
Deconsolidation of partially owned entity	(314,596)							(314,596)
Cash distributions to noncontrolling interests	(276)							(276)
Cash distributions declared ($0.8125 per common share, none of which represented a return of capital for federal income tax purposes)	(72,341)						(72,341)
Ending Balance at Mar. 31, 2018	$ 6,537,629	$ 221,932	$ 902	$ 4,776,594	$ (124,049)	$ 28,573	$ 1,583,833	$ 49,844
Ending Balance (in shares) at Mar. 31, 2018			89,135

Consolidated Statement of Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Stockholders' Equity [Abstract]
Cash distribution declared, per common share (in dollars per share)	$ 0.8125	$ 0.775

Consolidated Statement of Capital (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Partner's Capital
DRSPP proceeds	$ 42
Reallocation of noncontrolling interests in the operating partnership	3,645
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	3,102
Repurchases of common stock	(354,744)
Contribution to consolidated joint venture interests	157
Deconsolidation of partially owned entity	(314,596)
Cash distributions to noncontrolling interests	$ (276)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)	1
Deferred compensation plan and stock awards, net (in shares)	(19)
Repurchases of common stock (in shares)	(3,654)
Repurchases of common stock	$ (37)
Contributions - proceeds from stock options exercised (in shares)	4
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Contribution to consolidated joint venture interests	$ 157
Deconsolidation of partially owned entity	(314,596)
Cash distributions to noncontrolling interests	(276)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning Balance	6,589,454
Adjusted Balance	7,159,978
Net income	105,702
Other comprehensive income	9,969
Preferred distributions	(3,738)
DRSPP proceeds	42
Reallocation of noncontrolling interests in the operating partnership	3,645
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	3,102
Repurchases of common stock	(354,744)
Contribution to consolidated joint venture interests	157
Deconsolidation of partially owned entity	(314,596)
Contributions - proceeds from stock options exercised	729
Cash distributions to noncontrolling interests	(276)
Cash distributions declared ($0.8125 per common unit, none of which represented a return of capital for federal income tax purposes)	(72,341)
Ending Balance	6,537,629
SL Green Operating Partnership \| Common Stock \| Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 5,984,557
Beginning Balance (units)	92,803
Adjusted Balance	$ 6,555,081
Net income	105,504
Preferred distributions	$ (3,738)
DRSPP proceeds (in shares)	1
DRSPP proceeds	$ 42
Reallocation of noncontrolling interests in the operating partnership	$ 3,645
Deferred compensation plan and stock awards, net (in shares)	(19)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	$ 3,102
Repurchases of common stock (in shares)	(3,654)
Repurchases of common stock	$ (354,744)
Contributions - proceeds from stock options exercised (in shares)	4
Contributions - proceeds from stock options exercised	$ 729
Cash distributions declared ($0.8125 per common unit, none of which represented a return of capital for federal income tax purposes)	(72,341)
Ending Balance	$ 6,237,280
Ending Balance (units)	89,135
SL Green Operating Partnership \| Accumulated Other Comprehensive Income
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 18,604
Adjusted Balance	18,604
Other comprehensive income	9,969
Ending Balance	28,573
SL Green Operating Partnership \| Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning Balance	364,361
Adjusted Balance	364,361
Net income	198
Contribution to consolidated joint venture interests	157
Deconsolidation of partially owned entity	(314,596)
Cash distributions to noncontrolling interests	(276)
Ending Balance	49,844
Series I Preferred Stock \| SL Green Operating Partnership \| Preferred Units
Increase (Decrease) in Partner's Capital
Beginning Balance	221,932
Adjusted Balance	221,932
Ending Balance	$ 221,932
Accounting Standards Update 2014-09
Increase (Decrease) in Partner's Capital
Cumulative adjustment upon adoption of ASC 610-20		$ 570,524
Accounting Standards Update 2014-09 \| SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Cumulative adjustment upon adoption of ASC 610-20		570,524
Accounting Standards Update 2014-09 \| SL Green Operating Partnership \| Common Stock \| Partners' Interest
Increase (Decrease) in Partner's Capital
Cumulative adjustment upon adoption of ASC 610-20		$ 570,524

Consolidated Statement of Capital (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash distribution declared, per common share (in dollars per share)	$ 0.8125	$ 0.775
SL Green Operating Partnership
Cash distribution declared, per common share (in dollars per share)	$ 0.8125	$ 0.775

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net income	$ 113,823	$ 924
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	72,925	98,895
Equity in net income from unconsolidated joint ventures	(4,036)	(6,614)
Distributions of cumulative earnings from unconsolidated joint ventures	7,510	5,468
Equity in net loss (gain) on sale of interest in unconsolidated joint venture interest/real estate	6,440	(2,047)
Purchase price and other fair value adjustments	(49,293)	0
Depreciable real estate reserves	0	56,272
Gain on sale of real estate, net	(23,521)	(567)
Gain on sale of investments in marketable securities	0	(3,262)
Deferred rents receivable	(3,120)	(11,722)
Other non-cash adjustments	12,155	23,245
Changes in operating assets and liabilities:
Tenant and other receivables	(1,847)	1,272
Related party receivables	(4,567)	(3,211)
Deferred lease costs	(7,679)	(9,421)
Other assets	(47,826)	(45,356)
Accounts payable, accrued expenses, other liabilities and security deposits	18,890	(16,327)
Deferred revenue and land leases payable	4,692	25,600
Net cash provided by operating activities	94,546	113,149
Investing Activities
Acquisitions of real estate property	(1,276)	0
Additions to land, buildings and improvements	(51,631)	(101,090)
Acquisition deposits and deferred purchase price	(3,020)	0
Investments in unconsolidated joint ventures	(51,158)	(8,000)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	142,694	37,811
Net proceeds from disposition of real estate/joint venture interest	409,867	3,000
Proceeds from sale or redemption of marketable securities	0	54,363
Other investments	(21,687)	21,721
Origination of debt and preferred equity investments	(229,428)	(402,453)
Repayments or redemption of debt and preferred equity investments	261,641	411,969
Net cash provided by investing activities	456,002	17,321
Financing Activities
Proceeds from mortgages and other loans payable	99,115	778,445
Repayments of mortgages and other loans payable	(9,406)	(680,572)
Proceeds from revolving credit facility and senior unsecured notes	455,000	277,800
Repayments of revolving credit facility and senior unsecured notes	(495,000)	(277,800)
Proceeds from stock options exercised and DRIP issuance	771	8,808
Repurchase of common stock	(382,679)	(102)
Redemption of preferred stock	(150)	0
Distributions to noncontrolling interests in other partnerships	(276)	(469)
Contributions from noncontrolling interests in other partnerships	157	31,947
Distributions to noncontrolling interests in the Operating Partnership	(3,841)	(3,537)
Dividends / Distributions paid on common and preferred stock / units	(81,729)	(84,179)
Tax withholdings related to restricted share awards	(3,842)	(3,816)
Deferred loan costs and capitalized lease obligation	(429)	(7,712)
Net cash (used in) provided by financing activities	(422,309)	38,813
Net increase in cash, cash equivalents, and restricted cash	128,239	169,283
Cash, cash equivalents, and restricted cash at end of period	378,265	539,250
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership	15,448	18,240
Redemption of units in the Operating Partnership for stock	0	13,112
Derivative instruments at fair value	6,937	4,734
Tenant improvements and capital expenditures payable	15,952	7,087
Fair value adjustment to noncontrolling interest in Operating Partnership	3,645	15,548
Deconsolidation of subsidiaries	298,403	0
Transfer of assets related to assets held for sale	0	54,694
Transfer of liabilities related to assets held for sale	0	43
Deferred leasing payable	1,203	1,455
Removal of fully depreciated commercial real estate properties	106,142	2,043
Share repurchase payable	27,935	0
Total cash, cash equivalents, and restricted cash	378,265	539,250
SL Green Operating Partnership
Operating Activities
Net income	113,823	924
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	72,925	98,895
Equity in net income from unconsolidated joint ventures	(4,036)	(6,614)
Distributions of cumulative earnings from unconsolidated joint ventures	7,510	5,468
Equity in net loss (gain) on sale of interest in unconsolidated joint venture interest/real estate	6,440	(2,047)
Purchase price and other fair value adjustments	(49,293)	0
Depreciable real estate reserves	0	56,272
Gain on sale of real estate, net	(23,521)	(567)
Gain on sale of investments in marketable securities	0	(3,262)
Deferred rents receivable	(3,120)	(11,722)
Other non-cash adjustments	12,155	23,245
Changes in operating assets and liabilities:
Tenant and other receivables	(1,847)	1,272
Related party receivables	(4,567)	(3,211)
Deferred lease costs	(7,679)	(9,421)
Other assets	(47,826)	(45,356)
Accounts payable, accrued expenses, other liabilities and security deposits	18,890	(16,327)
Deferred revenue and land leases payable	4,692	25,600
Net cash provided by operating activities	94,546	113,149
Investing Activities
Acquisitions of real estate property	(1,276)	0
Additions to land, buildings and improvements	(51,631)	(101,090)
Acquisition deposits and deferred purchase price	(3,020)	0
Investments in unconsolidated joint ventures	(51,158)	(8,000)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	142,694	37,811
Net proceeds from disposition of real estate/joint venture interest	409,867	3,000
Proceeds from sale or redemption of marketable securities	0	54,363
Other investments	(21,687)	21,721
Origination of debt and preferred equity investments	(229,428)	(402,453)
Repayments or redemption of debt and preferred equity investments	261,641	411,969
Net cash provided by investing activities	456,002	17,321
Financing Activities
Proceeds from mortgages and other loans payable	99,115	778,445
Repayments of mortgages and other loans payable	(9,406)	(680,572)
Proceeds from revolving credit facility and senior unsecured notes	455,000	277,800
Repayments of revolving credit facility and senior unsecured notes	(495,000)	(277,800)
Proceeds from stock options exercised and DRIP issuance	771	8,808
Repurchase of common stock	(382,679)	(102)
Redemption of preferred stock	(150)	0
Distributions to noncontrolling interests in other partnerships	(276)	(469)
Contributions from noncontrolling interests in other partnerships	157	31,947
Dividends / Distributions paid on common and preferred stock / units	(85,570)	(87,716)
Tax withholdings related to restricted share awards	(3,842)	(3,816)
Deferred loan costs and capitalized lease obligation	(429)	(7,712)
Net cash (used in) provided by financing activities	(422,309)	38,813
Net increase in cash, cash equivalents, and restricted cash	128,239	169,283
Cash, cash equivalents, and restricted cash at beginning of year	250,026	369,967
Cash, cash equivalents, and restricted cash at end of period	378,265	539,250
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership	15,448	18,240
Redemption of units in the Operating Partnership for stock	0	13,112
Derivative instruments at fair value	6,937	4,734
Tenant improvements and capital expenditures payable	15,952	7,087
Fair value adjustment to noncontrolling interest in Operating Partnership	3,645	15,548
Deconsolidation of subsidiaries	298,403	0
Transfer of assets related to assets held for sale	0	54,694
Transfer of liabilities related to assets held for sale	0	43
Deferred leasing payable	1,203	1,455
Removal of fully depreciated commercial real estate properties	106,142	2,043
Share repurchase payable	27,935	0
Total cash, cash equivalents, and restricted cash	$ 250,026	$ 369,967

Organization and Basis of Presentation

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Basis of Presentation

SL Green Realty Corp., which is referred to as the Company or SL Green, a Maryland corporation, and SL Green Operating Partnership, L.P., which is referred to as SLGOP or the Operating Partnership, a Delaware limited partnership, were formed in June 1997 for the purpose of combining the commercial real estate business of S.L. Green Properties, Inc. and its affiliated partnerships and entities. The Operating Partnership received a contribution of interest in the real estate properties, as well as 95% of the economic interest in the management, leasing and construction companies which are referred to as the Service Corporation. All of the management, leasing and construction services that are provided to the properties that are wholly-owned by us and that are provided to certain joint ventures are conducted through SL Green Management LLC which is 100% owned by the Operating Partnership. The Company has qualified, and expects to qualify in the current fiscal year, as a real estate investment trust, or REIT, under the Internal Revenue Code of 1986, as amended, or the Code, and operates as a self-administered, self-managed REIT. A REIT is a legal entity that holds real estate interests and, through payments of dividends to stockholders, is permitted to minimize the payment of Federal income taxes at the corporate level. Unless the context requires otherwise, all references to "we," "our" and "us" means the Company and all entities owned or controlled by the Company, including the Operating Partnership.

Substantially all of our assets are held by, and all of our operations are conducted through, the Operating Partnership. The Company is the sole managing general partner of the Operating Partnership. As of March 31, 2018, noncontrolling investors held, in the aggregate, a 5.02% limited partnership interest in the Operating Partnership. We refer to these interests as the noncontrolling interests in the Operating Partnership. The Operating Partnership is considered a variable interest entity, or VIE, in which we are the primary beneficiary. See Note 11, "Noncontrolling Interests on the Company's Consolidated Financial Statements".

Reckson Associates Realty Corp., or Reckson, and Reckson Operating Partnership, L.P., or ROP, are wholly-owned subsidiaries of SL Green Realty Corp.

As of March 31, 2018, we owned the following interests in properties in the New York metropolitan area, primarily in midtown Manhattan. Our investments located outside of Manhattan are referred to as the Suburban properties:



		Consolidated			Unconsolidated		Total
Location	Property Type	Number of Properties		Approximate Square Feet (unaudited)	Number of Properties	Approximate Square Feet (unaudited)	Number of Properties	Approximate Square Feet (unaudited)	Weighted Average Occupancy(1) (unaudited)
Commercial:
Manhattan	Office	20		12,387,091	11	12,165,164	31	24,552,255	94.2	%
	Retail	4	(2)	302,583	9	347,970	13	650,553	94.2	%
	Development/Redevelopment	8		318,985	3	416,214	11	735,199	44.4	%
	Fee Interest	1		176,530	1	—	2	176,530	100.0	%
		33		13,185,189	24	12,929,348	57	26,114,537	92.8	%
Suburban	Office	20	(3)	3,013,200	2	640,000	22	3,653,200	83.1	%
	Retail	1		52,000	—	—	1	52,000	100.0	%
	Development/Redevelopment	1		1,000	1	—	2	1,000	—	%
		22		3,066,200	3	640,000	25	3,706,200	83.3	%
Total commercial properties		55		16,251,389	27	13,569,348	82	29,820,737	91.6	%
Residential:
Manhattan	Residential	3	(2)	472,105	10	2,156,751	13	2,628,856	88.9	%
Suburban	Residential	—		—	—	—	—	—	—	%
Total residential properties		3		472,105	10	2,156,751	13	2,628,856	88.9	%
Total portfolio		58		16,723,494	37	15,726,099	95	32,449,593	91.4	%


(1)	The weighted average occupancy for commercial properties represents the total occupied square feet divided by total square footage at acquisition. The weighted average occupancy for residential properties represents the total occupied units divided by total available units.

(2)

As of March 31, 2018, we owned a building at 315 West 33rd Street, also known as The Olivia, that was comprised of approximately 270,132 square feet (unaudited) of retail space and approximately 222,855 square feet (unaudited) of residential space. For the purpose of this report, we have included this building in the number of retail properties we own. However, we have included only the retail square footage in the retail approximate square footage, and have listed the balance of the square footage as residential square footage.


(3)	Includes the properties at 115-117 Stevens Avenue in Valhalla, New York, and 1-6 International Drive in Rye Brook, New York which are classified as held for sale at March 31, 2018.

As of March 31, 2018, we also managed an approximately 336,000 square foot (unaudited) office building owned by a third party and held debt and preferred equity investments with a book value of $2.1 billion, including $0.1 billion of debt and preferred equity investments and other financing receivables that are included in balance sheet line items other than the Debt and Preferred Equity Investments line item.

Partnership Agreement

In accordance with the partnership agreement of the Operating Partnership, or the Operating Partnership Agreement, we allocate all distributions and profits and losses in proportion to the percentage of ownership interests of the respective partners. As the managing general partner of the Operating Partnership, we are required to take such reasonable efforts, as determined by us in our sole discretion, to cause the Operating Partnership to distribute sufficient amounts to enable the payment of sufficient dividends by us to minimize any Federal income or excise tax at the Company level. Under the Operating Partnership Agreement, each limited partner has the right to redeem units of limited partnership interests for cash, or if we so elect, shares of SL Green's common stock on a one-for-one basis.

Basis of Quarterly Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by accounting principles generally accepted in the United States for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for the fair presentation of the financial position of the Company and the Operating Partnership at March 31, 2018 and the results of operations for the periods presented have been included. The operating results for the period presented are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Annual Report on Form 10-K for the year ended December 31, 2017 of the Company and the Operating Partnership.

The consolidated balance sheet at December 31, 2017 has been derived from the audited financial statements as of that date but does not include all the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.

Subsequent Events

In May 2018, the Company was the successful bidder for the leasehold interest at 2 Herald Square, at the foreclosure of the asset. The Company had purchased notes receivable secured by 2 Herald Square in April and May 2017. The loans were in maturity default at the time of acquisition and subsequently put on non-accrual in August 2017. No impairment had been recorded as the Company believed that the fair value of the property exceeded the carrying amount of the loans. The Company also reached an agreement to joint venture the asset with an Israeli-based institutional investor, subsequent to closing on the acquisition.

Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Significant Accounting Policies

Principles of Consolidation

The consolidated financial statements include our accounts and those of our subsidiaries, which are wholly-owned or controlled by us. Entities which we do not control through our voting interest and entities which are variable interest entities, but where we are not the primary beneficiary, are accounted for under the equity method. See Note 5, "Debt and Preferred Equity Investments" and Note 6, "Investments in Unconsolidated Joint Ventures." All significant intercompany balances and transactions have been eliminated.

We consolidate a variable interest entity, or VIE, in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE.

Investment in Commercial Real Estate Properties

We allocate the purchase price of real estate to land and building (inclusive of tenant improvements) and, if determined to be material, intangibles, such as the value of above- and below-market leases and origination costs associated with the in-place leases. We depreciate the amount allocated to building (inclusive of tenant improvements) over their estimated useful lives, which generally range from three to 40 years. We amortize the amount allocated to the above- and below-market leases over the remaining term of the associated lease, which generally range from one to 14 years, and record it as either an increase (in the case of below-market leases) or a decrease (in the case of above-market leases) to rental income. We amortize the amount allocated to the values associated with in-place leases over the expected term of the associated lease, which generally ranges from one to 14 years. If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The tenant improvements and origination costs are amortized as an expense over the remaining life of the lease (or charged against earnings if the lease is terminated prior to its contractual expiration date). We assess fair value of the leases based on estimated cash flow projections that utilize appropriate discount and capitalization rates and available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known trends, and market/economic conditions that may affect the property. To the extent acquired leases contain fixed rate renewal options that are below-market and determined to be material, we amortize such below-market lease value into rental income over the renewal period.

On a periodic basis, we assess whether there are any indications that the value of our real estate properties may be other than temporarily impaired or that their carrying value may not be recoverable. A property's value is considered impaired if management's estimate of the aggregate future cash flows (undiscounted) to be generated by the property is less than the carrying value of the property. To the extent impairment has occurred, the loss will be measured as the excess of the carrying amount of the property over the calculated fair value of the property. We also evaluate our real estate properties for impairment when a property has been classified as held for sale. Real estate assets held for sale are valued at the lower of their carrying value or fair value less costs to sell.

We recognized $2.4 million and $4.8 million of rental revenue for the three months ended March 31, 2018 and 2017 respectively, for the amortization of aggregate below-market leases in excess of above-market leases and a reduction in lease origination costs, resulting from the allocation of the purchase price of the applicable properties. For the three months ended March 31, 2018 and 2017, we recognized as a reduction to interest expense the amortization of above-market rate mortgages of $0.0 million and $0.7 million, respectively.

The following summarizes our identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases) as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Identified intangible assets (included in other assets):
Gross amount	$	282,288		$	325,880
Accumulated amortization	(241,043		)	(277,038		)
Net⁽¹⁾	$	41,245		$	48,842
Identified intangible liabilities (included in deferred revenue):
Gross amount	$	359,469		$	540,283
Accumulated amortization	(256,685		)	(402,583		)
Net⁽¹⁾	$	102,784		$	137,700


(1)	As of March 31, 2018 and December 31, 2017, $0.1 million and $13.9 million, respectively and $0.1 million and $4.1 million, respectively, of net intangible assets and net intangible liabilities, were reclassified to assets held for sale and liabilities related to assets held for sale.

Fair Value Measurements

See Note 16, "Fair Value Measurements."

Investment in Marketable Securities

At acquisition, we designate a debt security as held-to-maturity, available-for-sale, or trading. As of March 31, 2018, we did not have any debt securities designated as held-to-maturity or trading. We account for our available-for-sale debt securities at fair value pursuant to Accounting Standards Codification, or ASC, 820-10, with the net unrealized gains or losses reported as a component of accumulated other comprehensive income or loss. Any unrealized losses that are determined to be other-than-temporary are recognized in earnings up to their credit component.

The Company adopted ASU 2016-01 effective January 1, 2018 which required entities to measure investments in equity securities at fair value and recognize any changes in fair value in net income. Upon adoption we did not hold investments in equity securities and therefore did not record a cumulative-effect adjustment. We did not hold investments in equity securities as of March 31, 2018.

The cost of bonds and marketable securities sold is determined using the specific identification method.

At March 31, 2018 and December 31, 2017, we held the following marketable securities (in thousands):



	March 31, 2018		December 31, 2017
Commercial mortgage-backed securities	$	28,252	$	28,579
Total marketable securities available-for-sale	$	28,252	$	28,579

The cost basis of the commercial mortgage-backed securities was $27.5 million at both March 31, 2018 and December 31, 2017. These securities mature at various times through 2035. We held no equity marketable securities as of March 31, 2018 and December 31, 2017.

During the three months ended March 31, 2018, we did not dispose of any marketable securities. During the three months ended March 31, 2017, we disposed of marketable securities for aggregate net proceeds of $54.4 million and realized a gain of $3.3 million, which is included in gain on sale of investment in marketable securities on the consolidated statements of operations.

Investments in Unconsolidated Joint Ventures

We assess our investments in unconsolidated joint ventures for recoverability and if it is determined that a loss in value of the investment is other than temporary, we write down the investment to its fair value. We evaluate our equity investments for impairment based on the joint ventures' projected discounted cash flows. We do not believe that the values of any of our equity investments were impaired at March 31, 2018.

Reserve for Possible Credit Losses

The reserve for possible credit losses in connection with debt and preferred equity investments is the charge to earnings to increase the allowance for possible credit losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. Other factors considered include geographic trends, product diversification, the size of the portfolio and current economic conditions. Based upon these factors, we establish a provision for possible credit loss on each individual investment. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired.

Where impairment is indicated on an investment that is held to maturity, a valuation allowance is measured based upon the excess of the recorded investment amount over the fair value of the collateral. Any deficiency between the carrying amount of an asset and the calculated value of the collateral is charged to expense. We continue to assess or adjust our estimates based on circumstances of a loan and the underlying collateral. If additional information reflects increased recovery of our investment, we will adjust our reserves accordingly. There were no loan reserves recorded during the three months ended March 31, 2018 and 2017.

Debt and preferred equity investments held for sale are carried at the lower of cost or fair market value using available market information obtained through consultation with dealers or other originators of such investments as well as discounted cash flow models based on Level 3 data pursuant to ASC 820-10. As circumstances change, management may conclude not to sell an investment designated as held for sale. In such situations, the investment will be reclassified at its net carrying value to debt and preferred equity investments held to maturity. For these reclassified investments, the difference between the current carrying value and the expected cash to be collected at maturity will be accreted into income over the remaining term of the investment.

Income Taxes

SL Green is taxed as a REIT under Section 856(c) of the Code. As a REIT, SL Green generally is not subject to Federal income tax. To maintain its qualification as a REIT, SL Green must distribute at least 90% of its REIT taxable income to its stockholders and meet certain other requirements. If SL Green fails to qualify as a REIT in any taxable year, SL Green will be subject to Federal income tax on its taxable income at regular corporate rates. SL Green may also be subject to certain state, local and franchise taxes. Under certain circumstances, Federal income and excise taxes may be due on its undistributed taxable income.

The Operating Partnership is a partnership and, as a result, all income and losses of the partnership are allocated to the partners for inclusion in their respective income tax returns. The only provision for income taxes included in the consolidated statements of operations relates to the Operating Partnership’s consolidated taxable REIT subsidiaries. The Operating Partnership may also be subject to certain state, local and franchise taxes.

Pursuant to amendments to the Code that became effective January 1, 2001, we have elected, and may elect in the future, to treat certain of our existing or newly created corporate subsidiaries as taxable REIT subsidiaries, or TRSs. In general, TRSs may perform non-customary services for the tenants of the Company, hold assets that we cannot hold directly and generally may engage in any real estate or non-real estate related business. The TRSs generate income, resulting in Federal and state income tax liability for these entities.

During the three months ended March 31, 2018, we recorded Federal, state and local tax provisions of $0.5 million.

We follow a two-step approach for evaluating uncertain tax positions. Recognition (step one) occurs when an enterprise concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustained upon examination. Measurement (step two) determines the amount of benefit that is more-likely-than-not to be realized upon settlement. Derecognition of a tax position that was previously recognized would occur when a company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained. The use of a valuation allowance as a substitute for derecognition of tax positions is prohibited.

On December 22, 2017, the Tax Cuts and Jobs Act (the ‘‘Tax Act’’) was signed into law and makes substantial changes to the Code. Many of the provisions of the Tax Act will require guidance through the issuance of Treasury regulations in order to assess their effect. The Tax Act has not had a material impact on our financial statements.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Concentrations of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash investments, debt and preferred equity investments and accounts receivable. We place our cash investments with high quality financial institutions. The collateral securing our debt and preferred equity investments is located in the New York metropolitan area. See Note 5, "Debt and Preferred Equity Investments."

We perform ongoing credit evaluations of our tenants and require most tenants to provide security deposits or letters of credit. Though these security deposits and letters of credit are insufficient to meet the total value of a tenant's lease obligation, they are a measure of good faith and a source of funds to offset the economic costs associated with lost revenue and the costs associated with re-tenanting a space. The properties in our real estate portfolio are located in the New York metropolitan area. The tenants located in our buildings operate in various industries. Other than one tenant, Credit Suisse Securities (USA), Inc., who accounts for 8.2% of our share of annualized cash rent, no other tenant in our portfolio accounted for more than 5.0% of our share of annualized cash rent, including our share of joint venture annualized rent, at March 31, 2018. For the three months ended March 31, 2018, 7.3%, 7.3%, 6.3%, 5.8% and 5.7% of our annualized cash rent was attributable to 11 Madison Avenue, 1185 Avenue of the Americas, 420 Lexington Avenue, 1515 Broadway, and One Madison Avenue respectively. Annualized cash rent for all other consolidated properties was below 5.0%.

Reclassification

Certain prior year balances have been reclassified to conform to our current year presentation.

Accounting Standards Updates

In February 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-03, Technical Corrections and Improvements to Financial Instruments- Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. These amendments provide additional guidance related to equity securities without a readily determinable fair value, forward contracts and options purchased on those equity securities and fair value option liabilities. The guidance will be effective for the Company in the interim period beginning after June 15, 2018. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented.

In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities. The amendments in the new standard will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standard will also enhance the presentation of hedge results in the financial statements. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company has not yet adopted the guidance, and does not expect a material impact on the Company’s consolidated financial statements when the new standard is implemented.

In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting. The guidance clarifies the changes to the terms or conditions of a share-based payment award that require an entity to apply modification accounting in Topic 718. The Company adopted the guidance on January 1, 2018 and it had no impact on the Company's consolidated financial statements.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The guidance requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash. As a result, entities will no longer present transfers between these items on the statement of cash flows. The Company adopted the guidance on January 1, 2018 and has included the changes in restricted cash when reconciling the beginning-of-period and end-of-period total amounts on the statement of cash flows.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current ‘incurred loss’ model with an ‘expected loss’ approach. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 15, 2018. The Company has not yet adopted this new guidance and is currently evaluating the impact of adopting this new accounting standard on the Company’s consolidated financial statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases. The guidance requires lessees to recognize lease assets and lease liabilities for those leases classified as operating leases under the previous standard. Depending on the lease classification, lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The accounting applied by a lessor is largely unchanged from that applied under the previous standard. However, the presentation and disclosure in the financial statements of non-lease components such as charges to tenants for a building’s operating expenses has been updated. In January 2018, the FASB issued an exposure draft, Leases (Topic 842) Targeted Improvements, which would provide lessors with a practical expedient to not separate non-lease components from the related lease component under certain conditions. At the March 2018 Board meeting, the Board approved an amendment to the practical expedient. We anticipate the majority of our leases would qualify for the amended practical expedient. We expect this amended guidance to be finalized in 2018 and, as a result, we would adopt the practical expedient. Another impact is the measurement and presentation of ground leases under which the Company is lessee. The Company is required to record a liability for the obligation to make payments under the lease and an asset for the right to use the underlying asset during the lease term and will also apply the new expense recognition requirements given the lease classification. The Company is currently quantifying these impacts. The guidance is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company expects to adopt this guidance January 1, 2019 and will apply the modified retrospective approach.

In January 2016, the FASB issued ASU 2016-01 (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. The guidance requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value through earnings, to record changes in instrument-specific credit risk for financial liabilities measured under the fair value option in other comprehensive income, use the exit price notion when measuring an instrument’s fair value for disclosure and to separately present financial assets and liabilities by measurement category and form of instrument on the balance sheet or in the notes to the financial statements. The Company adopted the guidance effective January 1, 2018, and it had no impact on the Company’s consolidated financial statements.

In May 2014, the FASB issued a new comprehensive revenue recognition guidance which requires us to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods and services (ASU 2014-09). The FASB also issued implementation guidance in March 2016, April 2016 and May 2016 - ASU’s 2016-08, 2016-10 and 2016-12, respectively. The Company adopted this guidance on January 1, 2018. Since the Company’s revenue is related to leasing activities, the adoption of this guidance did not have a material impact on the consolidated financial statements. The new guidance is applicable to service contracts with joint ventures for which the Company earns property management fees, leasing commissions and development and construction fees. The adoption of this new guidance did not change the accounting for these fees as the pattern of recognition of revenue does not change with the new guidance. We will continue to recognize revenue over time on these contracts because the customer simultaneously receives and consumes the benefits provided by our performance.

In February 2017, the FASB issued ASU No. 2017-05 to clarify the scope of asset derecognition guidance in Subtopic 610-20, which also provided guidance on accounting for partial sales of nonfinancial assets. Subtopic 610-20 was issued in May 2014 as part of ASU 2014-09. The Company adopted this guidance on January 1, 2018, and applied the modified retrospective approach. The Company elected to adopt the practical expedient under ASC 606, Revenue from Contracts with Customers, which allows an entity to apply the guidance only to contracts with non-customers that are open based on ASU 360-20, Real Estate Sales, (i.e. failed sales) as of the adoption date. The Company had one open contract in 2017 with a non-customer that was evaluated under ASC 610-20. The Company entered into an agreement to sell a portion of their interest in an entity that held a controlling interest in the property at 1515 Broadway. Upon execution of the agreement in 2017, the transaction was evaluated under ASC 360-20, Real Estate Sales, and did not meet the criteria for sale accounting. Upon adoption of ASC 606, this contract met the criteria for sale accounting under ASC 610-20. Through the sale, the Company no longer retains a controlling interest, as defined in ASC 810, Consolidation, and the impact of this adjustment is a gain of $0.6 billion from the sale of the partial interest and related step-up in basis to fair value of the non-controlling interest retained. This was recorded in the first quarter of 2018 as an adjustment to beginning retained earnings.

Property Acquisitions	3 Months Ended
Property Acquisitions	Mar. 31, 2018
Business Combinations [Abstract]
Property Acquisitions	Property Acquisitions During the three months ended March 31, 2018, we did not acquire any properties from a third party.

Properties Held for Sale and Property Dispositions

3 Months Ended

Mar. 31, 2018

Discontinued Operations and Disposal Groups [Abstract]

Properties Held for Sale and Property Dispositions

Properties Held for Sale

During the three months ended March 31, 2018, we entered into agreements to sell the properties at 1-6 International Drive in Rye Brook, NY for a sale price of $55.0 million and the properties at 115-117 Stevens Avenue in Valhalla, New York, for a sales price of $12.0 million. We closed on the sale of 115-117 Stevens Avenue in May 2018.

As of March 31, 2018, 1-6 International Drive and 115-117 Stevens Avenue were classified as held for sale.

In May 2018, we reached an agreement to sell the fee interest at 635 Madison Avenue for a sales price of $151 million. We expect to record a $14 million charge in connection with the sale, which will be included in depreciable real estate reserves. The transaction, subject to certain closing conditions, is expected to be completed during the third quarter of 2018.

Property Dispositions

The following table summarizes the properties sold during the three months ended March 31, 2018:

Property

Disposition Date

Property Type

Approximate Square Feet

Sales Price⁽¹⁾

(in millions)

Gain

(in millions)

600 Lexington Avenue⁽²⁾

January 2018

Fee Interest

303,515

305.0

23.8


(1)	Sales price represents the gross sales price for a property or the gross asset valuation for interests in a property.


(2)	Gain on sale amounts do not include adjustments for expenses recorded in subsequent periods.

Debt and Preferred Equity Investments

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Debt and Preferred Equity Investments

Below is the rollforward analysis of the activity relating to our debt and preferred equity investments for the three months ended March 31, 2018 and the twelve months ended December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Balance at beginning of period ⁽¹⁾	$	2,114,041		$	1,640,412
Debt investment originations/accretion ⁽²⁾	233,370			1,142,591
Preferred equity investment originations/accretion ⁽²⁾	2,074			144,456
Redemptions/sales/syndications/amortization ⁽³⁾	(263,614		)	(813,418		)
Balance at end of period ⁽¹⁾	$	2,085,871		$	2,114,041


(1)	Net of unamortized fees, discounts, and premiums.


(2)	Accretion includes amortization of fees and discounts and paid-in-kind investment income.


(3)	Certain participations in debt investments that were sold or syndicated did not meet the conditions for sale accounting are included in other assets and other liabilities on the consolidated balance sheets.

Debt Investments

As of March 31, 2018 and December 31, 2017, we held the following debt investments with an aggregate weighted average current yield of 9.19%, excluding our investment in Two Herald Square, at March 31, 2018 (in thousands):



Loan Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Fixed Rate Investments:
Mortgage/Jr. Mortgage Loan⁽³⁾	$	—	$	—	$	250,464	$	250,464	April 2017
Mortgage Loan⁽⁴⁾	—		—		26,380		26,366		February 2019
Mortgage Loan	—		—		201		239		August 2019
Mezzanine Loan^(5a)	—		1,160,000		206,230		204,005		March 2020
Mezzanine Loan	—		15,000		3,500		3,500		September 2021
Mezzanine Loan	—		147,000		24,918		24,913		April 2022
Mezzanine Loan	—		280,000		35,074		34,600		August 2022
Mezzanine Loan	—		86,580		12,701		12,699		November 2023
Mezzanine Loan^(5b)	—		115,000		12,934		12,932		June 2024
Mezzanine Loan	—		95,000		30,000		30,000		January 2025
Mezzanine Loan	—		340,000		15,000		15,000		November 2026
Mezzanine Loan	—		1,657,500		55,250		55,250		June 2027
Total fixed rate	$	—	$	3,896,080	$	672,652	$	669,968
Floating Rate Investments:
Mezzanine Loan⁽⁶⁾	—		40,000		19,999		19,982		April 2018



Loan Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Mezzanine Loan⁽⁶⁾	—		75,014		23,346		34,947		April 2018
Mezzanine Loan	523		20,523		10,952		10,934		August 2018
Mortgage/Mezzanine Loan	—		—		19,965		19,940		August 2018
Mezzanine Loan	—		65,000		14,973		14,955		August 2018
Mortgage/Mezzanine Loan	—		—		16,980		16,969		September 2018
Mezzanine Loan	—		37,500		14,908		14,855		September 2018
Mortgage/Mezzanine Loan	391		—		23,609		23,609		October 2018
Mezzanine Loan	2,325		45,025		34,975		34,879		October 2018
Mezzanine Loan^(5c)	—		85,000		15,327		15,381		December 2018
Mezzanine Loan^(5d)	—		65,000		14,816		14,869		December 2018
Mezzanine Loan	—		33,000		26,947		26,927		December 2018
Mezzanine Loan	—		175,000		59,797		59,723		December 2018
Mezzanine Loan	—		45,000		12,192		12,174		January 2019
Mezzanine Loan	4,493		27,852		9,457		8,550		January 2019
Mezzanine Loan^(5e)(7)	795		—		15,150		15,148		March 2019
Mezzanine Loan	—		38,000		21,951		21,939		March 2019
Mezzanine Loan	—		175,000		37,307		37,250		April 2019
Mezzanine Loan	—		265,000		24,862		24,830		April 2019
Mortgage/Jr. Mortgage Participation Loan	24,587		208,094		74,944		71,832		August 2019
Mezzanine Loan	2,034		189,829		37,867		37,851		September 2019
Mortgage/Mezzanine Loan	22,570		—		146,517		143,919		September 2019
Mezzanine Loan	—		350,000		34,773		34,737		October 2019
Mortgage/Mezzanine Loan	1,792		—		66,026		—		December 2019
Mortgage/Mezzanine Loan	21,303		—		48,245		43,845		January 2020
Mezzanine Loan	1,592		568,461		77,927		75,834		January 2020
Mortgage Loan	16,038		—		83,465		—		February 2020
Mezzanine Loan	5,993		294,036		48,490		—		March 2020
Mezzanine Loan	6,654		35,112		11,539		11,259		July 2020
Mezzanine Loan	47,557		326,552		79,477		75,428		November 2020
Mortgage and Mezzanine Loan	40,798		—		90,789		88,989		December 2020
Mortgage and Mezzanine Loan	—		—		35,179		35,152		December 2020
Jr. Mortgage Participation/Mezzanine Loan	—		60,000		15,642		15,635		July 2021
Mortgage/Mezzanine Loan⁽⁸⁾	—		—		—		162,553		—
Mezzanine Loan⁽⁸⁾	—		—		—		74,755		—
Total floating rate	$	199,445	$	3,223,998	$	1,268,393	$	1,299,650
Total	$	199,445	$	7,120,078	$	1,941,045	$	1,969,618


(1)	Carrying value is net of discounts, premiums, original issue discounts and deferred origination fees.


(2)	Represents contractual maturity, excluding any unexercised extension options.

(3)

These loans were purchased at par in April and May 2017 and were in maturity default at the time of acquisition. At the time the loans were purchased, the Company expected to collect all contractually required payments, including interest. In August 2017, the Company determined that it was probable that the loans would not be repaid in full and therefore, the loans were put on non-accrual status. No impairment was recorded as the Company believes that the fair value of the property exceeds the carrying amount of the loans. As of March 31, 2018, the loans had an outstanding principal balance of $250.5 million and an accrued interest balance of $7.7 million.


(4)	In September 2014, we acquired a $26.4 million mortgage loan at a $0.2 million discount and a $5.7 million junior mortgage participation at a $5.7 million discount. The junior mortgage participation was a nonperforming loan at acquisition, is currently on non-accrual status and has no carrying value.


(5)	Carrying value is net of the following amounts that were sold or syndicated, which are included in other assets and other liabilities on the consolidated balance sheets as a result of the transfers not meeting the conditions for sale accounting: (a) $1.3 million, (b) $12.0 million, (c) $14.6 million, (d) $14.1 million, and (e) $5.1 million.


(6)	This loan was extended in April 2018.


(7)	This loan was extended in March 2018.


(8)	This loan was repaid in February 2018.

Preferred Equity Investments

As of March 31, 2018 and December 31, 2017, we held the following preferred equity investments with an aggregate weighted average current yield of 6.97% at March 31, 2018 (in thousands):



Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Preferred Equity	$	—	$	272,000	$	144,826	$	144,423	April 2021
Total	$	—	$	272,000	$	144,826	$	144,423


(1)	Carrying value is net of deferred origination fees.


(2)	Represents contractual maturity, excluding any unexercised extension options.

At March 31, 2018 and December 31, 2017, all debt and preferred equity investments were performing in accordance with the terms of the relevant investments, with the exception of a mortgage and junior mortgage participation that were purchased in maturity default in May 2017 and April 2017, respectively, as discussed in subnote 3 of the Debt Investments table above and a junior mortgage participation acquired in September 2014, which was acquired for zero and has a carrying value of zero, as discussed in subnote 4 of the Debt Investments table above.

We have determined that we have one portfolio segment of financing receivables at March 31, 2018 and 2017 comprising commercial real estate which is primarily recorded in debt and preferred equity investments. Included in other assets is an additional amount of financing receivables totaling $88.0 million and $65.5 million at March 31, 2018 and December 31, 2017, respectively. No financing receivables were 90 days past due at March 31, 2018, with the exception of a mortgage and junior mortgage participation purchased in maturity default in May 2017 and April 2017, respectively, as discussed in subnote 3 of the Debt Investments table above.

Investments in Unconsolidated Joint Ventures

3 Months Ended

Mar. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Investments in Unconsolidated Joint Ventures

We have investments in several real estate joint ventures with various partners. As of March 31, 2018 and December 31, 2017, 800 Third Avenue, 21 East 66th Street, 605 West 42^nd Street, 333 East 22nd Street, One Vanderbilt, and certain properties within the Stonehenge Portfolio are VIEs in which we are not the primary beneficiary. Our net equity investment in these VIEs was $631.4 million and $606.2 million as of March 31, 2018 and December 31, 2017, respectively. Our maximum loss is limited to the amount of our equity investment in these VIEs. See the "Principles of Consolidation" section of Note 2, "Significant Accounting Policies". All other investments below are voting interest entities. As we do not control the joint ventures listed below, we account for them under the equity method of accounting.

The table below provides general information on each of our joint ventures as of March 31, 2018:



Property	Partner	Ownership Interest⁽¹⁾	Economic Interest⁽¹⁾	Unaudited Approximate Square Feet	Acquisition Date⁽²⁾	Acquisition Price⁽²⁾(in thousands)
100 Park Avenue	Prudential Real Estate Investors	49.90%	49.90%	834,000	February 2000	$	95,800
717 Fifth Avenue	Jeff Sutton/Private Investor	10.92%	10.92%	119,500	September 2006	251,900
800 Third Avenue	Private Investors	60.52%	60.52%	526,000	December 2006	285,000
919 Third Avenue⁽³⁾	New York State Teacher's Retirement System	51.00%	51.00%	1,454,000	January 2007	1,256,727
1745 Broadway⁽⁴⁾	Ivanhoe Cambridge, Inc.	56.87%	56.87%	674,000	April 2007	520,000
Jericho Plaza⁽⁵⁾	Onyx Equities/Credit Suisse	11.67%	11.67%	640,000	April 2007	210,000
11 West 34th Street	Private Investor/ Jeff Sutton	30.00%	30.00%	17,150	December 2010	10,800
3 Columbus Circle⁽⁶⁾	The Moinian Group	48.90%	48.90%	741,500	January 2011	500,000
280 Park Avenue	Vornado Realty Trust	50.00%	50.00%	1,219,158	March 2011	400,000
1552-1560 Broadway⁽⁷⁾	Jeff Sutton	50.00%	50.00%	57,718	August 2011	136,550
724 Fifth Avenue	Jeff Sutton	50.00%	50.00%	65,010	January 2012	223,000
10 East 53rd Street	Canadian Pension Plan Investment Board	55.00%	55.00%	354,300	February 2012	252,500
521 Fifth Avenue	Plaza Global Real Estate Partners LP	50.50%	50.50%	460,000	November 2012	315,000
21 East 66th Street⁽⁸⁾	Private Investors	32.28%	32.28%	13,069	December 2012	75,000
650 Fifth Avenue⁽⁹⁾	Jeff Sutton	50.00%	50.00%	69,214	November 2013	—
121 Greene Street	Jeff Sutton	50.00%	50.00%	7,131	September 2014	27,400
175-225 Third Street Brooklyn, New York⁽¹⁰⁾	KCLW 3rd Street LLC/LIVWRK LLC	95.00%	95.00%	—	October 2014	74,600
55 West 46th Street	Prudential Real Estate Investors	25.00%	25.00%	347,000	November 2014	295,000
Stonehenge Portfolio⁽¹¹⁾	Various	Various	Various	1,439,016	February 2015	36,668
131-137 Spring Street	Invesco Real Estate	20.00%	20.00%	68,342	August 2015	277,750
605 West 42nd Street	The Moinian Group	20.00%	20.00%	927,358	April 2016	759,000
11 Madison Avenue	PGIM Real Estate	60.00%	60.00%	2,314,000	August 2016	2,605,000
333 East 22nd Street	Private Investors	33.33%	33.33%	26,926	August 2016	—
400 E 57th Street⁽¹²⁾	BlackRock, Inc and Stonehenge Partners	51.00%	41.00%	290,482	October 2016	170,000
One Vanderbilt⁽¹³⁾	National Pension Service of Korea/Hines Interest LP	71.01%	71.01%	—	January 2017	3,310,000
Mezzanine Loan⁽¹⁴⁾	Private Investors	33.33%	33.33%	—	May 2017	15,000
Worldwide Plaza	RXR Realty / New York REIT / Private Investor	24.35%	24.35%	2,048,725	October 2017	1,725,000
1515 Broadway⁽¹⁵⁾	Allianz Real Estate of America	56.87%	56.87%	1,750,000	November 2017	1,950,000


(1)	Ownership interest and economic interest represent the Company's interests in the joint venture as of March 31, 2018. Changes in ownership or economic interests within the current year are disclosed in the notes below.


(2)	Acquisition date and price represent the date on which the Company initially acquired an interest in the joint venture and the actual or implied gross purchase price for the joint venture on that date. Acquisition date and price are not adjusted for subsequent acquisitions or dispositions of interest.

(3)

In January 2018, the partnership agreement for our investment was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $49.3 million fair value adjustment in the consolidated statement of operations. This fair value was allocated to the assets and liabilities, including identified intangibles of the property.


(4)	In April 2018, the Company entered into an agreement to sell its interest in 1745 Broadway. The transaction is expected to close in the second quarter of 2018.


(5)	In April 2018, the Company entered into an agreement to sell its interest in Jericho Plaza. The transaction is expected to close in the second quarter of 2018.


(6)	As a result of the sale of a condominium interest in September 2012, Young & Rubicam, Inc., or Y&R, owns floors three through eight at the property. Because the joint venture has an option to repurchase these floors, the gain associated with this sale was deferred.


(7)	The purchase price represents only the purchase of the 1552 Broadway interest which comprised approximately 13,045 square feet. The joint venture also owns a long-term leasehold interest in the retail space and certain other spaces at 1560 Broadway, which is adjacent to 1552 Broadway.


(8)	We hold a 32.28% interest in three retail and two residential units at the property and a 16.14% interest in three residential units at the property.

(9)

The joint venture owns a long-term leasehold interest in the retail space at 650 Fifth Avenue. In connection with the ground lease obligation, SLG provided a performance guaranty and our joint venture partner executed a contribution agreement to reflect its pro rata obligation. In the event the property is converted into a condominium unit and the landlord elects the purchase option, the joint venture shall be obligated to acquire the unit at the then fair value.


(10)	In April 2018, the Company, together with its joint venture partners, closed on the sale of this property.


(11)	In February and March 2018, the Company, together with its joint venture partner, closed on the sale of two properties from the Stonehenge Portfolio. These sales are further described under Sale of Joint Venture Interest of Properties below.

(12)

In October 2016, the Company sold a 49% interest in this property to an investment account managed by BlackRock, Inc. The Company's interest in the property was sold within a consolidated joint venture owned 90% by the Company and 10% by Stonehenge. The transaction resulted in the deconsolidation of the venture's remaining 51% interest in the property. The Company's joint venture with Stonehenge remains consolidated resulting in the combined 51% interest being shown within investments in unconsolidated joint ventures on the Company's balance sheet.


(13)	The partners have committed aggregate equity totaling no less than $525 million and their ownership interest in the joint venture is based on their capital contributions, up to an aggregate maximum of 29.0%. At March 31, 2018 the total of the two partners' ownership interests based on equity contributed was 6.84%.

(14)

In May 2017, the Company contributed a mezzanine loan secured by a commercial property in midtown Manhattan to a joint venture and retained a 33.33% interest in the venture. The carrying value is net of $10.0 million that was sold, which is included in other assets and other liabilities on the consolidated balance sheets as a result of the transfers not meeting the conditions for sale accounting. The loan matures in November 2018.

(15)

In November 2017, the Company sold a 30% interest in 1515 Broadway to affiliates of Allianz Real Estate. The sale did not meet the criteria for sale accounting and as a result the property was accounted for under the profit sharing method at December 31, 2017. The Company achieved sale accounting upon adoption of ASC 610-20 in January 2018 and recorded a $0.6 billion gain from the sale of the partial interest and related step-up in basis to fair value of the retained non-controlling interest as an adjustment to beginning retained earnings based on the application of the modified retrospective adoption approach. The Company closed on the sale of an additional 13% interest in the property to Allianz in February 2018.

Acquisition, Development and Construction Arrangements

Based on the characteristics of the following arrangements, which are similar to those of an investment, combined with the expected residual profit of not greater than 50%, we have accounted for these debt and preferred equity investments under the equity method. As of March 31, 2018 and December 31, 2017, the carrying value for acquisition, development and construction arrangements were as follows (in thousands):



Loan Type	March 31, 2018		December 31, 2017		Maturity Date
Mezzanine Loan⁽¹⁾	$	44,751	$	44,823	February 2022
Mezzanine Loan⁽²⁾	27,628		26,716		July 2036
Mezzanine Loan and Preferred Equity⁽³⁾	—		100,000
	$	72,379	$	171,539


(1)	We have an option to convert our loan to an equity interest subject to certain conditions. We have determined that our option to convert the loan to equity is not a derivative financial instrument pursuant to GAAP.


(2)	The Company has the ability to convert this loan into an equity position starting in 2021 and the borrower is able to force this conversion in 2024.


(3)	The mezzanine loan was repaid and the preferred equity interest was redeemed in March 2018.

Sale of Joint Venture Interests or Properties

The following table summarizes the investments in unconsolidated joint ventures sold during the three months ended March 31, 2018:



Property	Ownership Interest	Disposition Date	Type of Sale	Gross Asset Valuation (in thousands)⁽¹⁾		Loss on Sale (in thousands)⁽²⁾
1274 Fifth Avenue⁽³⁾	9.83%	February 2018	Property	$	44,100	$	(362	)
1515 Broadway⁽⁴⁾	13.00%	February 2018	Ownership Interest	1,950,000		—
Stonehenge Village⁽³⁾	5.00%	March 2018	Property	287,000		(5,701		)


(1)	Represents implied gross valuation for the joint venture or sales price of the property.


(2)	Represents the Company's share of the loss.


(3)	Property was part of the Stonehenge Portfolio.


(4)	Our investment in 1515 Broadway was marked to fair value on January 1, 2018 upon adoption of ASC 610-20.

Joint Venture Mortgages and Other Loans Payable

We generally finance our joint ventures with non-recourse debt. In certain cases we have provided guarantees or master leases for tenant space, which terminate upon the satisfaction of specified circumstances or repayment of the underlying loans. The first mortgage notes and other loans payable collateralized by the respective joint venture properties and assignment of leases at March 31, 2018 and December 31, 2017, respectively, are as follows (amounts in thousands):



Property	Economic Interest ⁽¹⁾		Maturity Date	Interest Rate ⁽²⁾			March 31, 2018			December 31, 2017
Fixed Rate Debt:
521 Fifth Avenue	50.50	%	November 2019		3.73	%	$	170,000		$	170,000
717 Fifth Avenue ⁽³⁾	10.92	%	July 2022		4.45	%	300,000			300,000
717 Fifth Avenue ⁽³⁾	10.92	%	July 2022		5.50	%	355,328			355,328
650 Fifth Avenue ⁽⁴⁾	50.00	%	October 2022		4.46	%	210,000			210,000
650 Fifth Avenue ⁽⁴⁾	50.00	%	October 2022		5.45	%	65,000			65,000
21 East 66th Street	32.28	%	April 2023		3.60	%	12,000			12,000
919 Third Avenue	51.00	%	June 2023		5.12	%	500,000			—
3 Columbus Circle	48.90	%	March 2025		3.61	%	350,000			350,000
1515 Broadway	56.87	%	March 2025		3.93	%	868,309			872,528
11 Madison Avenue	60.00	%	September 2025		3.84	%	1,400,000			1,400,000
800 Third Avenue	60.52	%	February 2026		3.37	%	177,000			177,000
400 East 57th Street	41.00	%	November 2026		3.00	%	100,000			100,000
Worldwide Plaza	24.35	%	November 2027		3.98	%	1,200,000			1,200,000
Stonehenge Portfolio ⁽⁵⁾	Various		Various		4.25	%	306,990			357,282
Total fixed rate debt							$	6,014,627		$	5,569,138
Floating Rate Debt:
175-225 Third Street ⁽⁶⁾	95.00	%	June 2018	Prime+	1.00	%	$	40,000		$	40,000
Jericho Plaza ⁽⁷⁾	11.67	%	March 2019	L+	4.15	%	81,922			81,099
724 Fifth Avenue ⁽⁸⁾	50.00	%	April 2019	L+	2.42	%	275,000			275,000
280 Park Avenue	50.00	%	September 2019	L+	1.73	%	1,200,000			1,200,000
121 Greene Street	50.00	%	November 2019	L+	1.50	%	15,000			15,000
1745 Broadway ⁽⁹⁾	56.87	%	January 2020	L+	1.85	%	345,000			345,000
10 East 53rd Street	55.00	%	February 2020	L+	2.25	%	170,000			170,000
131-137 Spring Street	20.00	%	August 2020	L+	1.55	%	141,000			141,000
1552 Broadway	50.00	%	October 2020	L+	2.65	%	195,000			195,000
55 West 46th Street ⁽¹⁰⁾	25.00	%	November 2020	L+	2.13	%	172,511			171,444
11 West 34th Street	30.00	%	January 2021	L+	1.45	%	23,000			23,000
100 Park Avenue	49.90	%	February 2021	L+	1.75	%	360,000			360,000
One Vanderbilt ⁽¹¹⁾	71.01	%	September 2021	L+	3.50	%	375,000			355,535
605 West 42nd Street	20.00	%	August 2027	L+	1.44	%	550,000			550,000
21 East 66th Street	32.28	%	June 2033	1 Year Treasury+	2.75	%	1,628			1,648
Stonehenge Portfolio	Various		January 2021	L+	1.40	%	38,000			55,340
Total floating rate debt							$	3,983,061		$	3,979,066
Total joint venture mortgages and other loans payable							$	9,997,688		$	9,548,204
Deferred financing costs, net							(120,809		)	(136,103		)
Total joint venture mortgages and other loans payable, net							$	9,876,879		$	9,412,101


(1)	Economic interest represents the Company's interests in the joint venture as of March 31, 2018. Changes in ownership or economic interests, if any, within the current year are disclosed in the notes to the investment in unconsolidated joint ventures table above.


(2)	Interest rates as of March 31, 2018, taking into account interest rate hedges in effect during the period. Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.


(3)	These loans are comprised of a $300.0 million fixed rate mortgage loan and $355.3 million mezzanine loan. The mezzanine loan is subject to accretion based on the difference between contractual interest rate and contractual pay rate.


(4)	These loans are comprised of a $210.0 million fixed rate mortgage loan and $65.0 million fixed rate mezzanine loan.


(5)	Amount is comprised of $136.4 million and $170.6 million in fixed-rate mortgages that mature in August 2019 and June 2024, respectively.


(6)	In April 2018, along with our joint venture partner, we closed on the sale of the property.


(7)	The property secures a two year $100.0 million loan, of which $81.9 million is currently outstanding. In March 2018, we exercised a 12-month extension option.


(8)	In April 2018, we exercised a 12-month extension option.


(9)	This loan has a committed amount of $375.0 million, of which $30.0 million was unfunded as of March 31, 2018.


(10)	This loan has a committed amount of $195.0 million, of which $22.5 million was unfunded as of March 31, 2018.


(11)	This loan is a $1.5 billion construction facility, which bears interest at 350 basis points over 30-day LIBOR, with reductions based on meeting certain conditions, and has an initial five-year term with two one-year extension options. Advances under the loan are subject to incurred costs, funded equity, loan to value thresholds, and entering into construction contracts.

We act as the operating partner and day-to-day manager for all our joint ventures, except for Worldwide Plaza, 800 Third Avenue, Jericho Plaza, 280 Park Avenue, 3 Columbus Circle, 21 East 66th Street, 175-225 Third Street, 605 West 42nd Street, 400 East 57th Street, and the Stonehenge Portfolio. We are entitled to receive fees for providing management, leasing, construction supervision and asset management services to certain of our joint ventures. We earned $3.8 million and $5.4 million from these services, net of our ownership share of the joint ventures, for the three months ended March 31, 2018 and 2017, respectively. In addition, we have the ability to earn incentive fees based on the ultimate financial performance of certain of the joint venture properties.

The combined balance sheets for the unconsolidated joint ventures, at March 31, 2018 and December 31, 2017 are as follows (in thousands):



	March 31, 2018		December 31, 2017
Assets ⁽¹⁾
Commercial real estate property, net	$	14,652,483	$	12,822,133
Cash and restricted cash	452,648		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	359,396		349,944
Debt and preferred equity investments, net	103,379		202,539
Other assets	2,361,367		1,407,806
Total assets	$	17,929,273	$	15,277,331
Liabilities and equity ⁽¹⁾
Mortgages and other loans payable, net	$	9,876,879	$	9,412,101
Deferred revenue/gain	1,911,564		985,648
Other liabilities	493,369		411,053
Members' equity	5,647,461		4,468,529
Total liabilities and members' equity	$	17,929,273	$	15,277,331
Company's investments in unconsolidated joint ventures	$	3,034,596	$	2,362,989


(1)	The combined assets, liabilities and equity for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.

The combined statements of operations for the unconsolidated joint ventures, for the three months ended March 31, 2018 and 2017, are as follows (in thousands):



	Three Months Ended March 31,
	2018			2017
Total revenues	$	320,941		$	216,521
Operating expenses	59,773			38,794
Ground rent	4,393			4,251
Real estate taxes	57,027			34,939
Interest expense, net of interest income	89,741			55,328
Amortization of deferred financing costs	5,116			6,505
Transaction related costs	—			89
Depreciation and amortization	105,080			71,164
Total expenses	321,130			211,070
Net (loss) income before gain on sale ⁽¹⁾	$	(189	)	$	5,451
Company's equity in net income from unconsolidated joint ventures ⁽¹⁾	$	4,036		$	6,614


(1)	The combined statements of operation and the Company's equity in net income for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.

Deferred Costs

3 Months Ended

Mar. 31, 2018

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Deferred Costs

Deferred costs at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018			December 31, 2017
Deferred leasing costs	$	415,824		$	443,341
Less: accumulated amortization	(220,267		)	(217,140		)
Deferred costs, net	$	195,557		$	226,201

Mortgages and Other Loans Payable

3 Months Ended

Mar. 31, 2018

Mortgages and Other Loans Payable

Mortgages and other loans payable

Mortgages and Other Loans Payable

The first mortgages and other loans payable collateralized by the respective properties and assignment of leases or debt investments at March 31, 2018 and December 31, 2017, respectively, were as follows (amounts in thousands):



Property	Maturity Date	Interest Rate ⁽¹⁾			March 31, 2018			December 31, 2017
Fixed Rate Debt:
Unsecured Loan	June 2018		4.81	%	$	16,000		$	16,000
One Madison Avenue	May 2020		5.91	%	477,843			486,153
762 Madison Avenue	February 2022		5.00	%	771			771
100 Church Street	July 2022		4.68	%	216,240			217,273
420 Lexington Avenue	October 2024		3.99	%	300,000			300,000
400 East 58th Street ⁽²⁾	November 2026		3.00	%	40,000			40,000
Landmark Square	January 2027		4.90	%	100,000			100,000
485 Lexington Avenue	February 2027		4.25	%	450,000			450,000
1080 Amsterdam ⁽³⁾	February 2027		3.58	%	36,300			36,363
315 West 33rd Street	February 2027		4.17	%	250,000			250,000
Series J Preferred Units ⁽⁴⁾	April 2051		3.75	%	4,000			4,000
919 Third Avenue ⁽⁵⁾					—			500,000
Total fixed rate debt					$	1,891,154		$	2,400,560
Floating Rate Debt:
183, 187 Broadway & 5-7 Dey Street	May 2018	L+	2.70	%	$	58,000		$	58,000
2017 Master Repurchase Agreement	June 2018	L+	2.23	%	189,883			90,809
719 Seventh Avenue	February 2019	L+	3.05	%	42,143			41,622
220 East 42nd Street	October 2020	L+	1.60	%	275,000			275,000
Total floating rate debt					$	565,026		$	465,431
Total fixed rate and floating rate debt					$	2,456,180		$	2,865,991
Mortgages reclassed to liabilities related to assets held for sale					—			—
Total mortgages and other loans payable					$	2,456,180		$	2,865,991
Deferred financing costs, net of amortization					(22,186		)	(28,709		)
Total mortgages and other loans payable, net					$	2,433,994		$	2,837,282


(1)	Interest rate as of March 31, 2018, taking into account interest rate hedges in effect during the period. Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.


(2)	The loan carries a fixed interest rate of 300 basis points for the first five years and is prepayable without penalty at the end of year five.


(3)	The loan is comprised of a $35.5 million mortgage loan and $0.9 million subordinate loan with a fixed interest rate of 350 basis points and 700 basis points, respectively, for the first five years and is prepayable without penalty at the end of year five.

(4)

In connection with the acquisition of a commercial real estate property, the Operating Partnership issued $4.0 million, 3.75% Series J Preferred Units of limited partnership interest, or the Series J Preferred Units, with a mandatory liquidation preference of $1,000 per unit. The Series J Preferred Units are accounted for as debt because they can be redeemed in cash by the Operating Partnership on the earlier of (i) the date of the sale of the property or (ii) April 30, 2051 or at the option of the unitholders as provided for in the related agreement.


(5)	Our investment in the property was deconsolidated as of January 1, 2018. See Note 6, "Investments in Unconsolidated Joint Ventures".

At March 31, 2018 and December 31, 2017, the gross book value of the properties and debt and preferred equity investments collateralizing the mortgages and other loans payable, not including assets held for sale, was approximately $3.5 billion and $4.8 billion, respectively.

Master Repurchase Agreements

The Company has entered into two Master Repurchase Agreements, or MRAs, known as the 2016 MRA and 2017 MRA, which provide us with the ability to sell certain debt investments with a simultaneous agreement to repurchase the same at a certain date or on demand. We seek to mitigate risks associated with our repurchase agreement by managing the credit quality of our assets, early repayments, interest rate volatility, liquidity, and market value. The margin call provisions under our repurchase facilities permit valuation adjustments based on capital markets activity, and are not limited to collateral-specific credit marks. To monitor credit risk associated with our debt investments, our asset management team regularly reviews our investment portfolio and is in contact with our borrowers in order to monitor the collateral and enforce our rights as necessary. The risk associated with potential margin calls is further mitigated by our ability to recollateralize the facility with additional assets from our portfolio of debt investments, our ability to satisfy margin calls with cash or cash equivalents and our access to additional liquidity through the 2017 credit facility, as defined below.

In June 2017, we entered into the 2017 MRA, with a maximum facility capacity of $300.0 million. In April 2018, we increased the maximum facility capacity to $400.0 million. The facility bears interest on a floating rate basis at a spread to 30-day LIBOR based on the pledged collateral and advance rate and has an initial one year term, with two one year extension options. At March 31, 2018, the facility had an outstanding balance of $189.5 million, net of deferred financing costs.

In July 2016, we entered into a restated 2016 MRA, with a maximum facility capacity of $300.0 million. The facility bears interest ranging from 225 and 400 basis points over 30-day LIBOR depending on the pledged collateral and has an initial two-year term, with a one year extension option. Since December 6, 2015, we have been required to pay monthly in arrears a 25 basis point fee on the excess of $150.0 million over the average daily balance during the period when the average daily balance is less than $150.0 million. At March 31, 2018, the facility had no outstanding balance and a carrying value of $(0.6) million, representing deferred financing costs presented within other liabilities.

Corporate Indebtedness

2017 Credit Facility

In November 2017, we entered into an amendment to the credit facility, referred to as the 2017 credit facility, that was originally entered into by the Company in November 2012, or the 2012 credit facility. As of March 31, 2018, the 2017 credit facility consisted of a $1.5 billion revolving credit facility, a $1.3 billion term loan (or "Term Loan A"), and a $200.0 million term loan (or "Term Loan B") with maturity dates of March 31, 2022, March 31, 2023, and November 21, 2024, respectively. The revolving credit facility has two six-month as-of-right extension options to March 31, 2023. We also have an option, subject to customary conditions, to increase the capacity of the credit facility to $4.5 billion at any time prior to the maturity dates for the revolving credit facility and term loans without the consent of existing lenders, by obtaining additional commitments from our existing lenders and other financial institutions.

As of March 31, 2018, the 2017 credit facility bore interest at a spread over 30-day LIBOR ranging from (i) 82.5 basis points to 155 basis points for loans under the revolving credit facility, (ii) 90 basis points to 175 basis points for loans under Term Loan A, and (iii) 150 basis points to 245 basis points for loans under Term Loan B, in each case based on the credit rating assigned to the senior unsecured long term indebtedness of the Company.

At March 31, 2018, the applicable spread was 100 basis points for the revolving credit facility, 110 basis points for Term Loan A, and 165 basis points for Term Loan B. We are required to pay quarterly in arrears a 12.5 to 30 basis point facility fee on the total commitments under the revolving credit facility based on the credit rating assigned to the senior unsecured long term indebtedness of the Company. As of March 31, 2018, the facility fee was 20 basis points.

As of March 31, 2018, we had $11.8 million of outstanding letters of credit, zero drawn under the revolving credit facility and $1.5 billion outstanding under the term loan facilities, with total undrawn capacity of $1.5 billion under the 2017 credit facility. At March 31, 2018 and December 31, 2017, the revolving credit facility had a carrying value of $(9.2) million and $30.3 million, respectively, net of deferred financing costs. The March 31, 2018 carrying value represents deferred financing costs and is presented within other liabilities. At March 31, 2018 and December 31, 2017, the term loan facilities had a carrying value of $1.5 billion and $1.5 billion, respectively, net of deferred financing costs.

The Company and the Operating Partnership are borrowers jointly and severally obligated under the 2017 credit facility. ROP is a guarantor under the 2017 credit facility.

The 2017 credit facility includes certain restrictions and covenants (see Restrictive Covenants below).

Senior Unsecured Notes

The following table sets forth our senior unsecured notes and other related disclosures as of March 31, 2018 and December 31, 2017, respectively, by scheduled maturity date (amounts in thousands):



Issuance	March 31, 2018 Unpaid Principal Balance		March 31, 2018 Accreted Balance			December 31, 2017 Accreted Balance			Coupon Rate ⁽¹⁾		Initial Term (in Years)	Maturity Date
August 5, 2011 ⁽²⁾	$	250,000	$	249,972		$	249,953		5.00	%	7	August 2018
March 16, 2010 ⁽²⁾	250,000		250,000			250,000			7.75	%	10	March 2020
October 5, 2017 ⁽³⁾	500,000		499,514			499,489			3.25	%	5	October 2022
November 15, 2012 ⁽⁴⁾	300,000		304,920			305,163			4.50	%	10	December 2022
December 17, 2015 ⁽²⁾	100,000		100,000			100,000			4.27	%	10	December 2025
	$	1,400,000	$	1,404,406		$	1,404,605
Deferred financing costs, net			(8,086		)	(8,666		)
	$	1,400,000	$	1,396,320		$	1,395,939


(1)	Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates.


(2)	Issued by the Company, the Operating Partnership and ROP, as co-obligors.


(3)	Issued by the Operating Partnership with the Company and ROP as guarantors.


(4)	In October 2017, the Company, the Operating Partnership and ROP, as co-obligors, issued an additional $100.0 million of 4.50% senior unsecured notes due December 2022. The notes were priced at 105.334%.

Restrictive Covenants

The terms of the 2017 credit facility and certain of our senior unsecured notes include certain restrictions and covenants which may limit, among other things, our ability to pay dividends, make certain types of investments, incur additional indebtedness, incur liens and enter into negative pledge agreements and dispose of assets, and which require compliance with financial ratios relating to the maximum ratio of total indebtedness to total asset value, a minimum ratio of EBITDA to fixed charges, a maximum ratio of secured indebtedness to total asset value and a maximum ratio of unsecured indebtedness to unencumbered asset value. The dividend restriction referred to above provides that, we will not during any time when a default is continuing, make distributions with respect to common stock or other equity interests, except to enable the Company to continue to qualify as a REIT for Federal income tax purposes. As of March 31, 2018 and 2017, we were in compliance with all such covenants.

Junior Subordinated Deferrable Interest Debentures

In June 2005, the Company and the Operating Partnership issued $100.0 million in unsecured trust preferred securities through a newly formed trust, SL Green Capital Trust I, or the Trust, which is a wholly-owned subsidiary of the Operating Partnership. The securities mature in 2035 and bear interest at a floating rate of 125 basis points over the three-month LIBOR. Interest payments may be deferred for a period of up to eight consecutive quarters if the Operating Partnership exercises its right to defer such payments. The Trust preferred securities are redeemable at the option of the Operating Partnership, in whole or in part, with no prepayment premium. We do not consolidate the Trust even though it is a variable interest entity as we are not the primary beneficiary. Because the Trust is not consolidated, we have recorded the debt on our consolidated balance sheets and the related payments are classified as interest expense.

Principal Maturities

Combined aggregate principal maturities of mortgages and other loans payable, 2017 credit facility, trust preferred securities, senior unsecured notes and our share of joint venture debt as of March 31, 2018, including as-of-right extension options and put options, were as follows (in thousands):



	Scheduled Amortization		Principal		Revolving Credit Facility		Unsecured Term Loans		Trust Preferred Securities		Senior Unsecured Notes		Total		Joint Venture Debt
Remaining 2018	$	28,555	$	74,000	$	—	$	—	$	—	$	250,000	$	352,555	$	45,477
2019	42,271		42,143		—		—		—		—		84,414		262,460
2020	23,466		869,414		—		—		—		250,000		1,142,880		471,714
2021	11,638		—		—		—		—		—		11,638		454,571
2022	9,430		198,555		—		—		—		800,000		1,007,985		220,759
Thereafter	16,591		1,140,117		—		1,500,000		100,000		100,000		2,856,708		2,878,381
	$	131,951	$	2,324,229	$	—	$	1,500,000	$	100,000	$	1,400,000	$	5,456,180	$	4,333,362

Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands):



	Three Months Ended March 31,
	2018			2017
Interest expense before capitalized interest	$	54,918		$	72,422
Interest capitalized	(6,686		)	(6,279		)
Interest income	(316		)	(521		)
Interest expense, net	$	47,916		$	65,622

Corporate Indebtedness

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Corporate Indebtedness

Mortgages and Other Loans Payable



Property	Maturity Date	Interest Rate ⁽¹⁾			March 31, 2018			December 31, 2017
Fixed Rate Debt:
Unsecured Loan	June 2018		4.81	%	$	16,000		$	16,000
One Madison Avenue	May 2020		5.91	%	477,843			486,153
762 Madison Avenue	February 2022		5.00	%	771			771
100 Church Street	July 2022		4.68	%	216,240			217,273
420 Lexington Avenue	October 2024		3.99	%	300,000			300,000
400 East 58th Street ⁽²⁾	November 2026		3.00	%	40,000			40,000
Landmark Square	January 2027		4.90	%	100,000			100,000
485 Lexington Avenue	February 2027		4.25	%	450,000			450,000
1080 Amsterdam ⁽³⁾	February 2027		3.58	%	36,300			36,363
315 West 33rd Street	February 2027		4.17	%	250,000			250,000
Series J Preferred Units ⁽⁴⁾	April 2051		3.75	%	4,000			4,000
919 Third Avenue ⁽⁵⁾					—			500,000
Total fixed rate debt					$	1,891,154		$	2,400,560
Floating Rate Debt:
183, 187 Broadway & 5-7 Dey Street	May 2018	L+	2.70	%	$	58,000		$	58,000
2017 Master Repurchase Agreement	June 2018	L+	2.23	%	189,883			90,809
719 Seventh Avenue	February 2019	L+	3.05	%	42,143			41,622
220 East 42nd Street	October 2020	L+	1.60	%	275,000			275,000
Total floating rate debt					$	565,026		$	465,431
Total fixed rate and floating rate debt					$	2,456,180		$	2,865,991
Mortgages reclassed to liabilities related to assets held for sale					—			—
Total mortgages and other loans payable					$	2,456,180		$	2,865,991
Deferred financing costs, net of amortization					(22,186		)	(28,709		)
Total mortgages and other loans payable, net					$	2,433,994		$	2,837,282


(1)	Interest rate as of March 31, 2018, taking into account interest rate hedges in effect during the period. Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.


(2)	The loan carries a fixed interest rate of 300 basis points for the first five years and is prepayable without penalty at the end of year five.


(3)	The loan is comprised of a $35.5 million mortgage loan and $0.9 million subordinate loan with a fixed interest rate of 350 basis points and 700 basis points, respectively, for the first five years and is prepayable without penalty at the end of year five.

(4)


(5)	Our investment in the property was deconsolidated as of January 1, 2018. See Note 6, "Investments in Unconsolidated Joint Ventures".

Master Repurchase Agreements

Corporate Indebtedness

2017 Credit Facility

The Company and the Operating Partnership are borrowers jointly and severally obligated under the 2017 credit facility. ROP is a guarantor under the 2017 credit facility.

The 2017 credit facility includes certain restrictions and covenants (see Restrictive Covenants below).

Senior Unsecured Notes

The following table sets forth our senior unsecured notes and other related disclosures as of March 31, 2018 and December 31, 2017, respectively, by scheduled maturity date (amounts in thousands):



Issuance	March 31, 2018 Unpaid Principal Balance		March 31, 2018 Accreted Balance			December 31, 2017 Accreted Balance			Coupon Rate ⁽¹⁾		Initial Term (in Years)	Maturity Date
August 5, 2011 ⁽²⁾	$	250,000	$	249,972		$	249,953		5.00	%	7	August 2018
March 16, 2010 ⁽²⁾	250,000		250,000			250,000			7.75	%	10	March 2020
October 5, 2017 ⁽³⁾	500,000		499,514			499,489			3.25	%	5	October 2022
November 15, 2012 ⁽⁴⁾	300,000		304,920			305,163			4.50	%	10	December 2022
December 17, 2015 ⁽²⁾	100,000		100,000			100,000			4.27	%	10	December 2025
	$	1,400,000	$	1,404,406		$	1,404,605
Deferred financing costs, net			(8,086		)	(8,666		)
	$	1,400,000	$	1,396,320		$	1,395,939


(1)	Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates.


(2)	Issued by the Company, the Operating Partnership and ROP, as co-obligors.


(3)	Issued by the Operating Partnership with the Company and ROP as guarantors.


(4)	In October 2017, the Company, the Operating Partnership and ROP, as co-obligors, issued an additional $100.0 million of 4.50% senior unsecured notes due December 2022. The notes were priced at 105.334%.

Restrictive Covenants

Junior Subordinated Deferrable Interest Debentures

Principal Maturities



	Scheduled Amortization		Principal		Revolving Credit Facility		Unsecured Term Loans		Trust Preferred Securities		Senior Unsecured Notes		Total		Joint Venture Debt
Remaining 2018	$	28,555	$	74,000	$	—	$	—	$	—	$	250,000	$	352,555	$	45,477
2019	42,271		42,143		—		—		—		—		84,414		262,460
2020	23,466		869,414		—		—		—		250,000		1,142,880		471,714
2021	11,638		—		—		—		—		—		11,638		454,571
2022	9,430		198,555		—		—		—		800,000		1,007,985		220,759
Thereafter	16,591		1,140,117		—		1,500,000		100,000		100,000		2,856,708		2,878,381
	$	131,951	$	2,324,229	$	—	$	1,500,000	$	100,000	$	1,400,000	$	5,456,180	$	4,333,362

Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands):



	Three Months Ended March 31,
	2018			2017
Interest expense before capitalized interest	$	54,918		$	72,422
Interest capitalized	(6,686		)	(6,279		)
Interest income	(316		)	(521		)
Interest expense, net	$	47,916		$	65,622

Related Party Transactions

3 Months Ended

Mar. 31, 2018

Related Party Transactions

Cleaning/ Security/ Messenger and Restoration Services

Alliance Building Services, or Alliance, and its affiliates are partially owned by Gary Green, a son of Stephen L. Green, the chairman of our board of directors, and provide services to certain properties owned by us. Alliance’s affiliates include First Quality Maintenance, L.P., or First Quality, Classic Security LLC, Bright Star Couriers LLC and Onyx Restoration Works, and provide cleaning, extermination, security, messenger, and restoration services, respectively. In addition, First Quality has the non-exclusive opportunity to provide cleaning and related services to individual tenants at our properties on a basis separately negotiated with any tenant seeking such additional services. The Service Corporation has entered into an arrangement with Alliance whereby it will receive a profit participation above a certain threshold for services provided by Alliance to certain tenants at certain buildings above the base services specified in their lease agreements.

Income earned from the profit participation, which is included in other income on the consolidated statements of operations, was $1.0 million and $0.8 million for the three months ended March 31, 2018 and 2017, respectively.

We also recorded expenses, inclusive of capitalized expenses, of $4.0 million and $4.5 million for the three months ended March 31, 2018 and 2017, respectively, for these services (excluding services provided directly to tenants).

Management Fees

S.L. Green Management Corp., a consolidated entity, receives property management fees from an entity in which Stephen L. Green owns an interest. We received management fees from this entity of $0.1 million and $0.1 million for the three months ended March 31, 2018 and 2017, respectively.

One Vanderbilt Investment

In December 2016, we entered into agreements with entities owned and controlled by Marc Holliday and Andrew Mathias, pursuant to which they agreed to make an investment in our One Vanderbilt project at the appraised fair market value for the interests acquired. This investment entitles these entities to receive approximately 1.50% - 1.80% and 1.00% - 1.20%, respectively, of any profits realized by the Company from its One Vanderbilt project in excess of the Company’s capital contributions. The entities have no right to any return of capital. Accordingly, subject to previously disclosed repurchase rights, these interests will have no value and will not entitle these entities to any amounts (other than limited distributions to cover tax liabilities incurred) unless and until the Company has received distributions from the One Vanderbilt project in excess of the Company’s aggregate investment in the project. In the event that the Company does not realize a profit on its investment in the project (or would not realize a profit based on the value at the time the interests are repurchased), the entities owned and controlled by Messrs. Holliday and Mathias will lose the entire amount of their investment. The entities owned and controlled by Messrs. Holliday and Mathias paid $1.4 million and $1.0 million, respectively, which equal the fair market value of the interests acquired as of the date the investment agreements were entered into as determined by an independent third party appraisal that we obtained.

Other

We are entitled to receive fees for providing management, leasing, construction supervision and asset management services to certain of our joint ventures as further described in Note 6, "Investments in Unconsolidated Joint Ventures." Amounts due from joint ventures and related parties at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Due from joint ventures	$	21,972	$	15,025
Other	9,333		8,014
Related party receivables	$	31,305	$	23,039

Noncontrolling Interests on the Company's Consolidated Financial Statements

3 Months Ended

Mar. 31, 2018

Noncontrolling Interest [Abstract]

Noncontrolling Interests on the Company's Consolidated Financial Statements

Noncontrolling interests represent the common and preferred units of limited partnership interest in the Operating Partnership not held by the Company as well as third party equity interests in our other consolidated subsidiaries. Noncontrolling interests in the Operating Partnership are shown in the mezzanine equity while the noncontrolling interests in our other consolidated subsidiaries are shown in the equity section of the Company’s consolidated financial statements.

Common Units of Limited Partnership Interest in the Operating Partnership

As of March 31, 2018 and December 31, 2017, the noncontrolling interest unit holders owned 5.02%, or 4,715,338 units, and 4.58%, or 4,452,979 units, of the Operating Partnership, respectively. As of March 31, 2018, 4,715,338 shares of our common stock were reserved for issuance upon the redemption of units of limited partnership interest of the Operating Partnership.

Noncontrolling interests in the Operating Partnership is recorded at the greater of its cost basis or fair market value based on the closing stock price of our common stock at the end of the reporting period.

Below is the rollforward analysis of the activity relating to the noncontrolling interests in the Operating Partnership for the three months ended March 31, 2018 and the twelve months ended December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Balance at beginning of period	$	461,954		$	473,882
Distributions	(3,841		)	(14,266		)
Issuance of common units	15,448			25,723
Redemption of common units	—			(21,574		)
Net income	5,272			3,995
Accumulated other comprehensive income allocation	619			(94		)
Fair value adjustment	(3,645		)	(5,712		)
Balance at end of period	$	475,807		$	461,954

Preferred Units of Limited Partnership Interest in the Operating Partnership

The Operating Partnership has 1,902,000 4.50% Series G Preferred Units of limited partnership interest, or the Series G Preferred Units outstanding, with a liquidation preference of $25.00 per unit, which were issued in January 2012 in conjunction with an acquisition. The Series G Preferred unitholders receive annual dividends of $1.125 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series G Preferred Units are convertible into a number of common units of limited partnership interest in the Operating Partnership equal to (i) the liquidation preference plus accumulated and unpaid distributions on the conversion date divided by (ii) $88.50. The common units of limited partnership interest in the Operating Partnership may be redeemed in exchange for our common stock on a 1-to-1 basis. The Series G Preferred Units also provide the holder with the right to require the Operating Partnership to repurchase the Series G Preferred Units for cash before January 31, 2022.

The Operating Partnership has 60 Series F Preferred Units outstanding with a mandatory liquidation preference of $1,000.00 per unit.

The Operating Partnership has authorized up to 700,000 3.50% Series K Preferred Units of limited partnership interest, or the Series K Preferred Units, with a liquidation preference of $25.00 per unit. In August 2014, the Company issued 563,954 Series K Preferred Units in conjunction with an acquisition. The Series K Preferred unitholders receive annual dividends of $0.875 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series K Preferred Units can be redeemed at any time, at the option of the unitholder, either for cash or are convertible into a number of common units of limited partnership interest in the Operating Partnership equal to (i) the liquidation preference plus accumulated and unpaid distributions on the conversion date divided by (ii) $134.67.

The Operating Partnership has authorized up to 500,000 4.00% Series L Preferred Units of limited partnership interest, or the Series L Preferred Units, with a liquidation preference of $25.00 per unit. In August 2014, the Company issued 378,634 Series L Preferred Units in conjunction with an acquisition. The Series L Preferred unitholders receive annual dividends of $1.00 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series L Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

The Operating Partnership has authorized up to 1,600,000 3.75% Series M Preferred Units of limited partnership interest, or the Series M Preferred Units, with a liquidation preference of $25.00 per unit. In February 2015, the Company issued 1,600,000 Series M Preferred Units in conjunction with the acquisition of ownership interests in and relating to certain residential and retail real estate properties. The Series M Preferred unitholders receive annual dividends of $0.9375 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series M Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

The Operating Partnership has authorized up to 552,303 3.00% Series N Preferred Units of limited partnership interest, or the Series N Preferred Units, with a liquidation preference of $25.00 per unit. In June 2015, the Company issued 552,303 Series N Preferred Units in conjunction with an acquisition. The Series N Preferred unitholders receive annual dividends of $0.75 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series N Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

The Operating Partnership has authorized an aggregate of one 6.25% Series O Preferred Unit of limited partnership interest, or the Series O Preferred Unit. In June 2015, the Company issued the Series O Preferred Unit in connection with an acquisition.

The Operating Partnership has authorized up to 200,000 4.00% Series P Preferred Units of limited partnership interest, or the Series P Preferred Units, with a liquidation preference of $25.00 per unit. In July 2015, the Company issued 200,000 Series P Preferred Units in conjunction with an acquisition. The Series P Preferred unitholders receive annual dividends of $1.00 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series P Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

The Operating Partnership has authorized up to 268,000 3.50% Series Q Preferred Units of limited partnership interest, or the Series Q Preferred Units, with a liquidation preference of $25.00 per unit. In July 2015, the Company issued 268,000 Series Q Preferred Units in conjunction with an acquisition. The Series Q Preferred unitholders receive annual dividends of $0.875 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series Q Preferred Units can be redeemed at any time, at the option of the unitholder, either for cash or are convertible into a number of common units of limited partnership interest in the Operating Partnership equal to (i) the liquidation preference plus accumulated and unpaid distributions on the conversion date divided by (ii) $148.95.

The Operating Partnership has authorized up to 400,000 3.50% Series R Preferred Units of limited partnership interest, or the Series R Preferred Units, with a liquidation preference of $25.00 per unit. In August 2015, the Company issued 400,000 Series R Preferred Units in conjunction with an acquisition. The Series R Preferred unitholders receive annual dividends of $0.875 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series R Preferred Units can be redeemed at any time, at the option of the unitholder, either for cash or are convertible into a number of common units of limited partnership interest in the Operating Partnership equal to (i) the liquidation preference plus accumulated and unpaid distributions on the conversion date divided by (ii) $154.89.

The Operating Partnership has authorized up to 1,077,280 4.00% Series S Preferred Units of limited partnership interest, or the Series S Preferred Units, with a liquidation preference of $25.00 per unit. In August 2015, the Company issued 1,077,280 Series S Preferred Units in conjunction with an acquisition. The Series S Preferred unitholders receive annual dividends of $1.00 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series S Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

The Operating Partnership has authorized up to 230,000 2.75% Series T Preferred Units of limited partnership interest, or the Series T Preferred Units, with a liquidation preference of $25.00 per unit. In March 2016, the Company issued 230,000 Series T Preferred Units in conjunction with an acquisition. The Series T Preferred unitholders receive annual dividends of $0.6875 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Series T Preferred Units can be redeemed at any time at par, at the option of the unitholder, either for cash or are convertible into a number of common units of limited partnership interest in the Operating Partnership equal to (i) the liquidation preference plus accumulated and unpaid distributions on the conversion date divided by (ii) $119.02.

The Operating Partnership has authorized up to 680,000 4.50% Series U Preferred Units of limited partnership interest, or the Series U Preferred Units, with a liquidation preference of $25.00 per unit. In March 2016, the Company issued 680,000 Series U Preferred Units in conjunction with an acquisition. The Series U Preferred unitholders initially receive annual dividends of $1.125 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The annual dividend is subject to reduction upon the occurrence of certain circumstances set forth in the terms of the Series U Preferred Units. The minimum annual dividend is $0.75 per unit. The Series U Preferred Units can be redeemed at any time at par for cash at the option of the unitholder.

Through a consolidated subsidiary, we have authorized up to 109,161 3.50% Series A Preferred Units of limited partnership interest, or the Subsidiary Series A Preferred Units, with a liquidation preference of $1,000.00 per unit. In August 2015, the Company issued 109,161 Subsidiary Series A Preferred Units in conjunction with an acquisition. The Subsidiary Series A Preferred unitholders receive annual dividends of $35.00 per unit paid on a quarterly basis and dividends are cumulative, subject to certain provisions. The Subsidiary Series A Preferred Units can be redeemed at any time, at the option of the unitholder, either for cash or are convertible on a one-for-one basis, into the Series B Preferred Units of limited partnership interest, or the Subsidiary Series B Preferred Units. The Subsidiary Series B Preferred Units can be converted at any time, at the option of the unitholder, into a number of common stock equal to 6.71348 shares of common stock for each Subsidiary Series B Preferred Unit. As of March 31, 2018, no Subsidiary Series B Preferred Units have been issued.

Below is the rollforward analysis of the activity relating to the preferred units in the Operating Partnership for the three months ended March 31, 2018 and the twelve months ended December 31, 2017 (in thousands):



	March 31, 2018			December 31, 2017
Balance at beginning of period	$	301,735		$	302,010
Issuance of preferred units	—			—
Redemption of preferred units	(150		)	(275		)
Balance at end of period	$	301,585		$	301,735

Stockholders' Equity of the Company

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Stockholders' Equity of the Company

Stockholders’ Equity of the Company

Common Stock

Our authorized capital stock consists of 260,000,000 shares, $0.01 par value per share, consisting of 160,000,000 shares of common stock, $0.01 par value per share, 75,000,000 shares of excess stock, at $0.01 par value per share, and 25,000,000 shares of preferred stock, par value $0.01 per share. As of March 31, 2018, 89,135,009 shares of common stock and no shares of excess stock were issued and outstanding.

Stock Repurchase Program

In August 2016, our board of directors approved a stock repurchase plan under which we can buy up to $1.0 billion of shares of our common stock. In December 2017, our board of directors authorized an increase to the size of this plan by an additional $500 million of our common stock, bringing it to a total of $1.5 billion of shares of our common stock.

At March 31, 2018, repurchases under the plan were as follows:



Period	Shares repurchased	Average price paid per share	Cumulative number of shares repurchased as part of the repurchase plan or programs	Maximum approximate dollar value of shares that may yet be repurchased under the plan (in millions)⁽¹⁾
2017	8,342,411	$101.64	8,342,411	$652.0
First quarter 2018 ⁽²⁾	3,653,928	$97.07	11,996,339	$297.2


(1)	Reflective of $1.5 billion plan maximum as of March 31, 2018.


(2)	Includes 142,004 shares of common stock repurchased by the Company in March 2018 that were settled in April 2018.

Perpetual Preferred Stock

We have 9,200,000 shares of our 6.50% Series I Cumulative Redeemable Preferred Stock, or the Series I Preferred Stock, outstanding with a mandatory liquidation preference of $25.00 per share. The Series I Preferred stockholders receive annual dividends of $1.625 per share paid on a quarterly basis and dividends are cumulative, subject to certain provisions. We are entitled to redeem the Series I Preferred Stock at par for cash at our option. In August 2012, we received $221.9 million in net proceeds from the issuance of the Series I Preferred Stock, which were recorded net of underwriters' discount and issuance costs, and contributed the net proceeds to the Operating Partnership in exchange for 9,200,000 units of 6.50% Series I Cumulative Redeemable Preferred Units of limited partnership interest, or the Series I Preferred Units.

Dividend Reinvestment and Stock Purchase Plan ("DRSPP")

In February 2018, the Company filed a registration statement with the SEC for our dividend reinvestment and stock purchase plan, or DRSPP, which automatically became effective upon filing. The Company registered 3,500,000 shares of our common stock under the DRSPP. The DRSPP commenced on September 24, 2001.

Earnings per Share

SL Green's earnings per share for the three months ended March 31, 2018 and 2017 are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic Earnings:
Income attributable to SL Green common stockholders	$	101,766	$	11,351
Effect of Dilutive Securities:
Redemption of units to common shares	5,272		476
Diluted Earnings:
Income attributable to SL Green common stockholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic Shares:
Weighted average common stock outstanding	90,520	100,643
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares	4,683	4,607
Stock-based compensation plans	53	304
Diluted weighted average common stock outstanding	95,256	105,554

SL Green has excluded 1,210,802 and 1,025,419 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2018 and 2017, respectively, as they were anti-dilutive.

Accumulated Other Comprehensive Income

The following tables set forth the changes in accumulated other comprehensive income (loss) by component as of March 31, 2018 (in thousands):



	Net unrealized gain on derivative instruments ⁽¹⁾		SL Green’s share of joint venture net unrealized gain on derivative instruments ⁽²⁾		Net unrealized gain on marketable securities			Total
Balance at December 31, 2017	$	12,542	$	5,020	$	1,042		$	18,604
Other comprehensive (loss) income before reclassifications	6,859		3,114		(315		)	9,658
Amounts reclassified from accumulated other comprehensive income	310		1		—			311
Balance at March 31, 2018	$	19,711	$	8,135	$	727		$	28,573

(1)

Amount reclassified from accumulated other comprehensive income (loss) is included in interest expense in the respective consolidated statements of operations. As of March 31, 2018 and December 31, 2017, the deferred net losses from these terminated hedges, which is included in accumulated other comprehensive loss relating to net unrealized loss on derivative instrument, was $2.7 million and $3.2 million, respectively.


(2)	Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net income from unconsolidated joint ventures in the respective consolidated statements of operations.

Partners' Capital of the Operating Partnership

3 Months Ended

Mar. 31, 2018

Stockholders' Equity

Partners' Capital of the Operating Partnership

Stockholders’ Equity of the Company

Common Stock

Stock Repurchase Program

At March 31, 2018, repurchases under the plan were as follows:



Period	Shares repurchased	Average price paid per share	Cumulative number of shares repurchased as part of the repurchase plan or programs	Maximum approximate dollar value of shares that may yet be repurchased under the plan (in millions)⁽¹⁾
2017	8,342,411	$101.64	8,342,411	$652.0
First quarter 2018 ⁽²⁾	3,653,928	$97.07	11,996,339	$297.2


(1)	Reflective of $1.5 billion plan maximum as of March 31, 2018.


(2)	Includes 142,004 shares of common stock repurchased by the Company in March 2018 that were settled in April 2018.

Perpetual Preferred Stock

Dividend Reinvestment and Stock Purchase Plan ("DRSPP")

Earnings per Share

SL Green's earnings per share for the three months ended March 31, 2018 and 2017 are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic Earnings:
Income attributable to SL Green common stockholders	$	101,766	$	11,351
Effect of Dilutive Securities:
Redemption of units to common shares	5,272		476
Diluted Earnings:
Income attributable to SL Green common stockholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic Shares:
Weighted average common stock outstanding	90,520	100,643
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares	4,683	4,607
Stock-based compensation plans	53	304
Diluted weighted average common stock outstanding	95,256	105,554

Accumulated Other Comprehensive Income

The following tables set forth the changes in accumulated other comprehensive income (loss) by component as of March 31, 2018 (in thousands):



	Net unrealized gain on derivative instruments ⁽¹⁾		SL Green’s share of joint venture net unrealized gain on derivative instruments ⁽²⁾		Net unrealized gain on marketable securities			Total
Balance at December 31, 2017	$	12,542	$	5,020	$	1,042		$	18,604
Other comprehensive (loss) income before reclassifications	6,859		3,114		(315		)	9,658
Amounts reclassified from accumulated other comprehensive income	310		1		—			311
Balance at March 31, 2018	$	19,711	$	8,135	$	727		$	28,573

(1)


(2)	Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net income from unconsolidated joint ventures in the respective consolidated statements of operations.

SL Green Operating Partnership

Stockholders' Equity

Partners' Capital of the Operating Partnership

The Company is the sole general partner of the Operating Partnership and at March 31, 2018 owned 89,135,009 general and limited partnership interests in the Operating Partnership and 9,200,000 Series I Preferred Units. Partnership interests in the Operating Partnership are denominated as “common units of limited partnership interest” (also referred to as “OP Units”) or “preferred units of limited partnership interest” (also referred to as “Preferred Units”). All references to OP Units and Preferred Units outstanding exclude such units held by the Company. A holder of an OP Unit may present such OP Unit to the Operating Partnership for redemption at any time (subject to restrictions agreed upon at the issuance of OP Units to particular holders that may restrict such right for a period of time, generally one year from issuance). Upon presentation of an OP Unit for redemption, the Operating Partnership must redeem such OP Unit in exchange for the cash equal to the then value of a share of common stock of the Company, except that the Company may, at its election, in lieu of cash redemption, acquire such OP Unit for one share of common stock. Because the number of shares of common stock outstanding at all times equals the number of OP Units that the Company owns, one share of common stock is generally the economic equivalent of one OP Unit, and the quarterly distribution that may be paid to the holder of an OP Unit equals the quarterly dividend that may be paid to the holder of a share of common stock. Each series of Preferred Units makes a distribution that is set in accordance with an amendment to the partnership agreement of the Operating Partnership. Preferred Units may also be convertible into OP Units at the election of the holder thereof or the Company, subject to the terms of such Preferred Units.

Net income (loss) allocated to the preferred unitholders and common unitholders reflects their pro rata share of net income (loss) and distributions.

Limited Partner Units

As of March 31, 2018, limited partners other than SL Green owned 5.02%, or 4,715,338 common units, of the Operating Partnership.

Preferred Units

Preferred units not owned by SL Green are further described in Note 11, “Noncontrolling Interests on the Company’s Consolidated Financial Statements - Preferred Units of Limited Partnership Interest in the Operating Partnership.”

Earnings per Unit

The Operating Partnership's earnings per unit for the three months ended March 31, 2018 and 2017, respectively, are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic and Diluted Earnings:
Income attributable to SLGOP common unitholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic units:
Weighted average common units outstanding	95,203	105,250
Effect of Dilutive Securities:
Stock-based compensation plans	53	304
Diluted weighted average common units outstanding	95,256	105,554

The Operating Partnership has excluded 1,210,802 and 1,025,419 common unit equivalents from the diluted units outstanding for the three months ended March 31, 2018 and 2017, respectively, as they were anti-dilutive.

Share-based Compensation

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-based Compensation

We have stock-based employee and director compensation plans. Our employees are compensated through the Operating Partnership. Under each plan, whenever the Company issues common or preferred stock, the Operating Partnership issues an equivalent number of units of limited partnership interest of a corresponding class to the Company.

Fourth Amended and Restated 2005 Stock Option and Incentive Plan

The Fourth Amended and Restated 2005 Stock Option and Incentive Plan, or the 2005 Plan, was approved by the Company's board of directors in April 2016 and its stockholders in June 2016 at the Company's annual meeting of stockholders. The 2005 Plan authorizes the issuance of stock options, stock appreciation rights, unrestricted and restricted stock, phantom shares, dividend equivalent rights, cash-based awards and other equity-based awards. Subject to adjustments upon certain corporate transactions or events, awards with respect to up to a maximum of 27,030,000 fungible units may be granted under the 2005 Plan. Currently, different types of awards count against the limit on the number of fungible units differently, with (1) full-value awards (i.e., those that deliver the full value of the award upon vesting, such as restricted stock) counting as 3.74 Fungible Units per share subject to such awards, (2) stock options, stock appreciation rights and other awards that do not deliver full value and expire five years from the date of grant counting as 0.73 fungible units per share subject to such awards, and (3) all other awards (e.g., ten-year stock options) counting as 1.0 fungible units per share subject to such awards. Awards granted under the 2005 Plan prior to the approval of the fourth amendment and restatement in June 2016 continue to count against the fungible unit limit based on the ratios that were in effect at the time such awards were granted, which may be different than the current ratios. As a result, depending on the types of awards issued, the 2005 Plan may result in the issuance of more or less than 27,030,000 shares. If a stock option or other award granted under the 2005 Plan expires or terminates, the common stock subject to any portion of the award that expires or terminates without having been exercised or paid, as the case may be, will again become available for the issuance of additional awards. Shares of our common stock distributed under the 2005 Plan may be treasury shares or authorized but unissued shares. Currently, unless the 2005 Plan has been previously terminated by the Company's board of directors, new awards may be granted under the 2005 Plan until June 2, 2026, which is the tenth anniversary of the date that the 2005 Plan was most recently approved by the Company's stockholders. As of March 31, 2018, 7.3 million fungible units were available for issuance under the 2005 Plan after reserving for shares underlying outstanding restricted stock units, phantom stock units granted pursuant to our Non-Employee Directors' Deferral Program and LTIP Units.

Options are granted under the plan with an exercise price at the fair market value of the Company's common stock on the date of grant and, subject to employment, generally expire five or ten years from the date of grant, are not transferable other than on death, and generally vest in one to five years commencing one year from the date of grant. We have also granted Class O LTIP Units, which are a class of LTIP Units in the Operating Partnership structured to provide economics similar to those of stock options. Class O LTIP Units, once vested, may be converted, at the election of the holder, into a number of common units of the Operating Partnership per Class O LTIP Unit determined by the increase in value of a share of the Company’s common stock at the time of conversion over a participation threshold, which equals the fair market value of a share of the Company’s common stock at the time of grant. Class O LTIP Units are entitled to distributions, subject to vesting, equal per unit to 10% of the per unit distributions paid with respect to the common units of the Operating Partnership.

The fair value of each stock option or LTIP Unit granted is estimated on the date of grant using the Black-Scholes option pricing model based on historical information with the following weighted average assumptions for grants during the three months ended March 31, 2018 and the year ended December 31, 2017.



	March 31, 2018		December 31, 2017
Dividend yield	2.85	%	2.51	%
Expected life	3.5 years		4.4 years
Risk-free interest rate	2.48	%	1.73	%
Expected stock price volatility	22.00	%	28.10	%

A summary of the status of the Company's stock options as of March 31, 2018 and December 31, 2017, and changes during the three months ended March 31, 2018 and year ended December 31, 2017 are as follows:



	March 31, 2018					December 31, 2017
	Options Outstanding			Weighted Average Exercise Price		Options Outstanding			Weighted Average Exercise Price
Balance at beginning of period	1,548,719			$	101.48	1,737,213			$	98.44
Granted	6,000			97.91		174,000			105.66
Exercised	(4,000		)	88.91		(292,193		)	81.07
Lapsed or canceled	(18,799		)	111.39		(70,301		)	121.68
Balance at end of period	1,531,920			$	101.37	1,548,719			$	101.48
Options exercisable at end of period	1,040,103			$	98.25	800,902			$	94.33
Total fair value of options granted during the period	$	84,068				$	3,816,652

All options were granted with strike prices ranging from $20.67 to $137.18. The remaining weighted average contractual life of the options outstanding was 3.4 years and the remaining average contractual life of the options exercisable was 2.9 years.

During the three months ended March 31, 2018 and 2017, we recognized compensation expense for these options of $1.6 million and $2.0 million, respectively. As of March 31, 2018, there was $6.7 million of total unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted average period of 1.2 years.

Stock-based Compensation

Effective January 1, 1999, the Company implemented a deferred compensation plan, or the Deferred Plan, where shares issued under the Deferred Plan were granted to certain employees, including our executives and vesting will occur annually upon the completion of a service period or our meeting established financial performance criteria. Annual vesting occurs at rates ranging from 15% to 35% once performance criteria are reached.

A summary of the Company's restricted stock as of March 31, 2018 and December 31, 2017 and charges during the three months ended March 31, 2018 and the year ended December 31, 2017, are as follows:



	March 31, 2018			December 31, 2017
Balance at beginning of period	3,298,216			3,202,031
Granted	33,450			96,185
Canceled	(4,550		)	—
Balance at end of period	3,327,116			3,298,216
Vested during the period	91,014			95,736
Compensation expense recorded	$	3,134,975		$	9,809,749
Total fair value of restricted stock granted during the period	$	3,237,006		$	9,905,986

The fair value of restricted stock that vested during the three months ended March 31, 2018 and the year ended December 31, 2017 was $9.7 million and $9.4 million, respectively. As of March 31, 2018 there was $18.1 million of total unrecognized compensation cost related to restricted stock, which is expected to be recognized over a weighted average period of 2.0 years.

For the three months ended March 31, 2018 and 2017, $1.6 million and $1.6 million, respectively, was capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options.

We granted LTIP Units, which include bonus, time-based and performance based awards, with a fair value of $20.6 million and $20.5 million as of March 31, 2018 and December 31, 2017, respectively. The grant date fair value of the LTIP Unit awards was calculated in accordance with ASC 718. A third party consultant determined the fair value of the LTIP Units to have a discount from our common stock price. The discount was calculated by considering the inherent uncertainty that the LTIP Units will reach parity with other common partnership units and the illiquidity due to transfer restrictions. As of March 31, 2018, there was $9.7 million of total unrecognized compensation expense related to the time-based and performance based awards, which is expected to be recognized over a weighted average period of 1.2 years.

During the three months ended March 31, 2018 and 2017, we recorded compensation expense related to bonus, time-based and performance based awards of $6.9 million and $10.0 million, respectively.

2014 Outperformance Plan

In August 2014, the compensation committee of the Company's board of directors approved the general terms of the SL Green Realty Corp. 2014 Outperformance Plan, or the 2014 Outperformance Plan. Participants in the 2014 Outperformance Plan could earn, in the aggregate, up to 610,000 LTIP Units in our Operating Partnership based on our total return to stockholders for the three-year period beginning September 1, 2014. Under the 2014 Outperformance Plan, two-thirds of the LTIP Units were subject to performance based vesting based on the Company’s absolute total return to stockholders and one-third of the LTIP Units were subject to performance based vesting based on relative total return to stockholders compared to the constituents of the MSCI REIT Index. LTIP Units earned under the 2014 Outperformance Plan were to be subject to continued vesting requirements, with 50% of any awards earned vesting on August 31, 2017 and the remaining 50% vesting on August 31, 2018, subject to continued employment with us through such dates. Participants were not entitled to distributions with respect to LTIP Units granted under the 2014 Outperformance Plan unless and until they are earned. If LTIP Units were earned, each participant would have been entitled to the distributions that would have been paid had the number of earned LTIP Units been issued at the beginning of the performance period, with such distributions being paid in the form of cash or additional LTIP Units. Thereafter, distributions were to be paid currently with respect to all earned LTIP Units, whether vested or unvested.

Based on our performance, none of the LTIP Units granted under the 2014 Outperformance Plan were earned pursuant to the terms of the 2014 Outperformance Plan, and all units issued were forfeited in 2017.

The cost of the 2014 Outperformance Plan ($27.9 million, subject to forfeitures), based on the portion of the 2014 Outperformance Plan granted prior to termination, was amortized into earnings through December 31, 2017. We recorded no compensation expense for the three months ended March 31, 2018 and compensation expense of $2.1 million for the three months ended March 31, 2017 related to the 2014 Outperformance Plan.

Deferred Compensation Plan for Directors

Under our Non-Employee Director's Deferral Program, which commenced July 2004, the Company's non-employee directors may elect to defer up to 100% of their annual retainer fee, chairman fees, meeting fees and annual stock grant. Unless otherwise elected by a participant, fees deferred under the program shall be credited in the form of phantom stock units. The program provides that a director's phantom stock units generally will be settled in an equal number of shares of common stock upon the earlier of (i) the January 1 coincident with or the next following such director's termination of service from the Board of Directors or (ii) a change in control by us, as defined by the program. Phantom stock units are credited to each non-employee director quarterly using the closing price of our common stock on the first business day of the respective quarter. Each participating non-employee director is also credited with dividend equivalents or phantom stock units based on the dividend rate for each quarter, which are either paid in cash currently or credited to the director’s account as additional phantom stock units.

During the three months ended March 31, 2018, 10,211 phantom stock units and 9,266 shares of common stock were issued to our board of directors. We recorded compensation expense of $2.2 million and $1.9 million during the three months ended March 31, 2018 and 2017, respectively, related to the Deferred Compensation Plan.

As of March 31, 2018, there were 110,064 phantom stock units outstanding pursuant to our Non-Employee Director's Deferral Program.

Employee Stock Purchase Plan

In 2007, the Company's board of directors adopted the 2008 Employee Stock Purchase Plan, or ESPP, to encourage our employees to increase their efforts to make our business more successful by providing equity-based incentives to eligible employees. The ESPP is intended to qualify as an "employee stock purchase plan" under Section 423 of the Code, and has been adopted by the board to enable our eligible employees to purchase the Company's shares of common stock through payroll deductions. The ESPP became effective on January 1, 2008 with a maximum of 500,000 shares of the common stock available for issuance, subject to adjustment upon a merger, reorganization, stock split or other similar corporate change. The Company filed a registration statement on Form S-8 with the SEC with respect to the ESPP. The common stock is offered for purchase through a series of successive offering periods. Each offering period will be three months in duration and will begin on the first day of each calendar quarter, with the first offering period having commenced on January 1, 2008. The ESPP provides for eligible employees to purchase the common stock at a purchase price equal to 85% of the lesser of (1) the market value of the common stock on the first day of the offering period or (2) the market value of the common stock on the last day of the offering period. The ESPP was approved by our stockholders at our 2008 annual meeting of stockholders. As of March 31, 2018, 107,193 shares of our common stock had been issued under the ESPP.

Accumulated Other Comprehensive Income

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Accumulated Other Comprehensive Income

Stockholders’ Equity of the Company

Common Stock

Stock Repurchase Program

At March 31, 2018, repurchases under the plan were as follows:



Period	Shares repurchased	Average price paid per share	Cumulative number of shares repurchased as part of the repurchase plan or programs	Maximum approximate dollar value of shares that may yet be repurchased under the plan (in millions)⁽¹⁾
2017	8,342,411	$101.64	8,342,411	$652.0
First quarter 2018 ⁽²⁾	3,653,928	$97.07	11,996,339	$297.2


(1)	Reflective of $1.5 billion plan maximum as of March 31, 2018.


(2)	Includes 142,004 shares of common stock repurchased by the Company in March 2018 that were settled in April 2018.

Perpetual Preferred Stock

Dividend Reinvestment and Stock Purchase Plan ("DRSPP")

Earnings per Share

SL Green's earnings per share for the three months ended March 31, 2018 and 2017 are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic Earnings:
Income attributable to SL Green common stockholders	$	101,766	$	11,351
Effect of Dilutive Securities:
Redemption of units to common shares	5,272		476
Diluted Earnings:
Income attributable to SL Green common stockholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic Shares:
Weighted average common stock outstanding	90,520	100,643
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares	4,683	4,607
Stock-based compensation plans	53	304
Diluted weighted average common stock outstanding	95,256	105,554

Accumulated Other Comprehensive Income

The following tables set forth the changes in accumulated other comprehensive income (loss) by component as of March 31, 2018 (in thousands):



	Net unrealized gain on derivative instruments ⁽¹⁾		SL Green’s share of joint venture net unrealized gain on derivative instruments ⁽²⁾		Net unrealized gain on marketable securities			Total
Balance at December 31, 2017	$	12,542	$	5,020	$	1,042		$	18,604
Other comprehensive (loss) income before reclassifications	6,859		3,114		(315		)	9,658
Amounts reclassified from accumulated other comprehensive income	310		1		—			311
Balance at March 31, 2018	$	19,711	$	8,135	$	727		$	28,573

(1)


(2)	Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net income from unconsolidated joint ventures in the respective consolidated statements of operations.

Fair Value Measurements

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

We are required to disclose fair value information with regard to our financial instruments, whether or not recognized in the consolidated balance sheets, for which it is practical to estimate fair value. The FASB guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. We measure and/or disclose the estimated fair value of financial assets and liabilities based on a hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity and the reporting entity’s own assumptions about market participant assumptions. This hierarchy consists of three broad levels: Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date; Level 2 - inputs other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly; and Level 3 - unobservable inputs for the asset or liability that are used when little or no market data is available. We follow this hierarchy for our assets and liabilities measured at fair value on a recurring and nonrecurring basis. In instances in which the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level of input that is significant to the fair value measurement in its entirety. Our assessment of the significance of the particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability.

The following tables set forth the assets and liabilities that we measure at fair value on a recurring and non-recurring basis by their levels in the fair value hierarchy at March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Marketable securities	$	28,252	$	—	$	28,252	$	—
Interest rate cap and swap agreements (included in other assets)	$	23,629	$	—	$	23,629	$	—



	December 31, 2017
	Total		Level 1		Level 2		Level 3
Assets:
Marketable securities	$	28,579	$	—	$	28,579	$	—
Interest rate cap and swap agreements (included in other assets)	$	16,692	$	—	$	16,692	$	—

We determine other than temporary impairment in real estate investments and debt and preferred equity investments, including intangibles primarily utilizing cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs.

As of March 31, 2018, we held notes receivable with an outstanding principal balance of $250.5 million and an accrued interest balance of $7.7 million, which were purchased at par, and were in maturity default at the time of acquisition. In August 2017, the Company determined that it was probable that the loans would not be repaid in full and therefore, the loans were put on non-accrual status. The Company has initiated proceedings to foreclose on the property, and expects to take control of the property unless the buyer is able to repay the principal and interest, including default interest and fees, on the notes receivable in full prior to the completion of the foreclosure process. We believe the collateral value is sufficient to recover the carrying amounts of the notes receivable.

In January 2018, the partnership agreement for our investment in 919 Third Avenue was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $49.3 million fair value adjustment in the consolidated statement of operations. This fair value was determined using a third party valuation which primarily utilized cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs.

Marketable securities classified as Level 1 are derived from quoted prices in active markets. The valuation technique used to measure the fair value of marketable securities classified as Level 2 were valued based on quoted market prices or model driven valuations using the significant inputs derived from or corroborated by observable market data. Marketable securities in an unrealized loss position are not considered to be other than temporarily impaired. We do not intend to sell these securities and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases.

The fair value of derivative instruments is based on current market data received from financial sources that trade such instruments and are based on prevailing market data and derived from third party proprietary models based on well-recognized financial principles and reasonable estimates about relevant future market conditions, which are classified as Level 2 inputs.

The financial assets and liabilities that are not measured at fair value on our consolidated balance sheets include cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, debt and preferred equity investments, mortgages and other loans payable and other secured and unsecured debt. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable, and accounts payable and accrued expenses reported in our consolidated balance sheets approximates fair value due to the short term nature of these instruments. The fair value of debt and preferred equity investments, which is classified as Level 3, is estimated by discounting the future cash flows using current interest rates at which similar loans with the same maturities would be made to borrowers with similar credit ratings. The fair value of borrowings, which is classified as Level 3, is estimated by discounting the contractual cash flows of each debt instrument to their present value using adjusted market interest rates, which is provided by a third-party specialist.

The following table provides the carrying value and fair value of these financial instruments as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018				December 31, 2017
	Carrying Value⁽¹⁾		Fair Value		Carrying Value⁽¹⁾		Fair Value

Debt and preferred equity investments	$	2,085,871	⁽²⁾		$	2,114,041	⁽²⁾

Fixed rate debt	$	3,795,560	$	3,840,843	$	4,305,165	$	4,421,866
Variable rate debt	1,665,026		1,673,313		1,605,431		1,612,224
	$	5,460,586	$	5,514,156	$	5,910,596	$	6,034,090


(1)	Amounts exclude net deferred financing costs.


(2)	At both March 31, 2018 and December 31, 2017, debt and preferred equity investments had an estimated fair value ranging between $2.1 billion and $2.3 billion.

Disclosure about fair value of financial instruments was based on pertinent information available to us as of March 31, 2018 and December 31, 2017. Although we are not aware of any factors that would significantly affect the reasonable fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since that date and current estimates of fair value may differ significantly from the amounts presented herein.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Financial Instruments: Derivatives and Hedging

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Financial Instruments: Derivatives and Hedging

In the normal course of business, we use a variety of commonly used derivative instruments, such as interest rate swaps, caps, collar and floors, to manage, or hedge interest rate risk. We hedge our exposure to variability in future cash flows for forecasted transactions in addition to anticipated future interest payments on existing debt. We recognize all derivatives on the balance sheet at fair value. Derivatives that are not hedges are adjusted to fair value through earnings. If a derivative is a hedge, depending on the nature of the hedge, changes in the fair value of the derivative will either be offset against the change in fair value of the hedge asset, liability, or firm commitment through earnings, or recognized in other comprehensive income until the hedged item is recognized in earnings. The ineffective portion of a derivative's change in fair value will be immediately recognized in earnings. Reported net income and equity may increase or decrease prospectively, depending on future levels of interest rates and other variables affecting the fair values of derivative instruments and hedged items, but will have no effect on cash flows. Currently, all of our designated derivative instruments are effective hedging instruments.

The following table summarizes the notional value at inception and fair value of our consolidated derivative financial instruments at March 31, 2018 based on Level 2 information. The notional value is an indication of the extent of our involvement in these instruments at that time, but does not represent exposure to credit, interest rate or market risks (amounts in thousands).



	Notional Value		Strike Rate		Effective Date	Expiration Date	Balance Sheet Location	Fair Value
Interest Rate Swap	$	200,000	1.131	%	July 2016	July 2023	Other Assets	$	14,149
Interest Rate Swap	100,000		1.161	%	July 2016	July 2023	Other Assets	6,927
Interest Rate Cap	137,500		4.000	%	September 2017	September 2019	Other Assets	19
Interest Rate Swap	100,000		1.928	%	December 2017	November 2020	Other Assets	1,273
Interest Rate Swap	100,000		1.934	%	December 2017	November 2020	Other Assets	1,260
								$	23,628

During the three months ended March 31, 2018, we recorded a loss on the changes in the fair value of $0.2 million, which is included in interest expense in the consolidated statements of operations. During the three months ended March 31, 2017, we recorded a loss on the changes in the fair value of $0.1 million, which is included in interest expense in the consolidated statements of operations.

The Company has agreements with each of its derivative counterparties that contain a provision where if the Company either defaults or is capable of being declared in default on any of its indebtedness, then the Company could also be declared in default on its derivative obligations. As of March 31, 2018, the fair value of derivatives in a net liability position including accrued interest but excluding any adjustment for nonperformance risk related to these agreements was zero. As of March 31, 2018, the Company has not posted any collateral related to these agreements and was not in breach of any agreement provisions. If the Company had breached any of these provisions, it could have been required to settle its obligations under the agreements at their aggregate termination value of zero at March 31, 2018.

Gains and losses on terminated hedges are included in accumulated other comprehensive income, and are recognized into earnings over the term of the related mortgage obligation. Over time, the realized and unrealized gains and losses held in accumulated other comprehensive income will be reclassified into earnings as an adjustment to interest expense in the same periods in which the hedged interest payments affect earnings. We estimate that $1.3 million of the current balance held in accumulated other comprehensive income will be reclassified into interest expense and $1.0 million of the portion related to our share of joint venture accumulated other comprehensive income will be reclassified into equity in net income from unconsolidated joint ventures within the next 12 months.

The following table presents the effect of our derivative financial instruments and our share of our joint ventures' derivative financial instruments that are designated and qualify as hedging instruments on the consolidated statements of operations for the three months ended March 31, 2018 and 2017, respectively (in thousands):



	Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion)					Location of (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income	Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)				Location of (Loss) Recognized in Income on Derivative	Amount of (Loss) Recognized into Income (Ineffective Portion)
	Three Months Ended March 31,						Three Months Ended March 31,					Three Months Ended March 31,
Derivative	2018		2017				2018		2017			2018			2017
Interest Rate Swaps/Caps	$	7,282	$	(3,137	)	Interest expense	$	329	$	979	Interest expense	$	(9	)	$	(8	)
Share of unconsolidated joint ventures' derivative instruments	3,313		341			Equity in net income from unconsolidated joint ventures	1		399		Equity in net income from unconsolidated joint ventures	(89		)	(95		)
	$	10,595	$	(2,796	)		$	330	$	1,378		$	(98	)	$	(103	)

Commitments and Contingencies

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Legal Proceedings

As of March 31, 2018, the Company and the Operating Partnership were not involved in any material litigation nor, to management's knowledge, was any material litigation threatened against us or our portfolio which if adversely determined could have a material adverse impact on us.

Environmental Matters

Our management believes that the properties are in compliance in all material respects with applicable Federal, state and local ordinances and regulations regarding environmental issues. Management is not aware of any environmental liability that it believes would have a materially adverse impact on our financial position, results of operations or cash flows. Management is unaware of any instances in which it would incur significant environmental cost if any of our properties were sold.

Capital and Ground Leases Arrangements

The following is a schedule of future minimum lease payments under capital leases and non-cancellable operating leases with initial terms in excess of one year as of March 31, 2018 (in thousands):



	Capital lease			Non-cancellable operating leases
Remaining 2018	$	1,790		$	23,286
2019	2,411			31,066
2020	2,620			31,437
2021	2,794			31,628
2022	2,794			29,472
2023	2,794			27,166
Thereafter	817,100			676,088
Total minimum lease payments	$	832,303		$	850,143
Amount representing interest	(789,274		)
Capital lease obligations	$	43,029

Segment Information

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Segment Information

The Company has two reportable segments, real estate and debt and preferred equity investments. We evaluate real estate performance and allocate resources based on earnings contribution to income from continuing operations.

The primary sources of revenue are generated from tenant rents and escalations and reimbursement revenue. Real estate property operating expenses consist primarily of security, maintenance, utility costs, insurance, real estate taxes and ground rent expense (at certain applicable properties). See Note 5, "Debt and Preferred Equity Investments," for additional details on our debt and preferred equity investments.

Selected consolidated results of operations for the three months ended March 31, 2018 and 2017, and selected asset information as of March 31, 2018 and December 31, 2017, regarding our operating segments are as follows (in thousands):



	Real Estate Segment		Debt and Preferred Equity Segment		Total Company
Total revenues
Three months ended:
March 31, 2018	$	256,405	$	45,290	$	301,695
March 31, 2017	337,082		40,299		377,381
Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities
Three months ended:
March 31, 2018	$	14,024	$	33,425	$	47,449
March 31, 2017	13,807		37,513		51,320
Total assets
As of:
March 31, 2018	$	11,144,740	$	2,236,130	$	13,380,870
December 31, 2017	11,643,261		2,339,643		13,982,904

Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities represents total revenues less total expenses for the real estate segment and total investment income less allocated interest expense for the debt and preferred equity segment. Interest costs for the debt and preferred equity segment includes actual costs incurred for borrowings on the 2016 MRA and 2017 MRA. Interest is imputed on the investments that do not collateralize the 2016 MRA or 2017 MRA using our corporate borrowing cost. We also allocate loan loss reserves, net of recoveries, and transaction related costs to the debt and preferred equity segment. We do not allocate marketing, general and administrative expenses to the debt and preferred equity segment since the use of personnel and resources is dependent on transaction volume between the two segments and varies period over period. In addition, we base performance on the individual segments prior to allocating marketing, general and administrative expenses. For the three months ended March 31, 2018, and 2017, marketing, general and administrative expenses totaled $23.5 million, and $24.1 million respectively. All other expenses, except interest, relate entirely to the real estate assets.

There were no transactions between the above two segments.

The table below reconciles net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities to net income for the three months ended March 31, 2018 and 2017 (in thousands):



	Three Months Ended March 31,
	2018			2017
Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities	$	47,449		$	51,320
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440		)	2,047
Purchase price and other fair value adjustments	49,293			—
Gain on sale of real estate, net	23,521			567
Depreciable real estate reserves	—			(56,272		)
Gain on sale of investment in marketable securities	—			3,262
Net income	$	113,823		$	924

Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include our accounts and those of our subsidiaries, which are wholly-owned or controlled by us. Entities which we do not control through our voting interest and entities which are variable interest entities, but where we are not the primary beneficiary, are accounted for under the equity method. See Note 5, "Debt and Preferred Equity Investments" and Note 6, "Investments in Unconsolidated Joint Ventures." All significant intercompany balances and transactions have been eliminated. We consolidate a variable interest entity, or VIE, in which we are considered the primary beneficiary. The primary beneficiary is the entity that has (i) the power to direct the activities that most significantly impact the entity's economic performance and (ii) the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE.
Investment in Commercial Real Estate Properties	Investment in Commercial Real Estate Properties We allocate the purchase price of real estate to land and building (inclusive of tenant improvements) and, if determined to be material, intangibles, such as the value of above- and below-market leases and origination costs associated with the in-place leases. We depreciate the amount allocated to building (inclusive of tenant improvements) over their estimated useful lives, which generally range from three to 40 years. We amortize the amount allocated to the above- and below-market leases over the remaining term of the associated lease, which generally range from one to 14 years, and record it as either an increase (in the case of below-market leases) or a decrease (in the case of above-market leases) to rental income. We amortize the amount allocated to the values associated with in-place leases over the expected term of the associated lease, which generally ranges from one to 14 years. If a tenant vacates its space prior to the contractual termination of the lease and no rental payments are being made on the lease, any unamortized balance of the related intangible will be written off. The tenant improvements and origination costs are amortized as an expense over the remaining life of the lease (or charged against earnings if the lease is terminated prior to its contractual expiration date). We assess fair value of the leases based on estimated cash flow projections that utilize appropriate discount and capitalization rates and available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known trends, and market/economic conditions that may affect the property. To the extent acquired leases contain fixed rate renewal options that are below-market and determined to be material, we amortize such below-market lease value into rental income over the renewal period.
Fair Value Measurements	Fair Value Measurements We are required to disclose fair value information with regard to our financial instruments, whether or not recognized in the consolidated balance sheets, for which it is practical to estimate fair value. The FASB guidance defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. We measure and/or disclose the estimated fair value of financial assets and liabilities based on a hierarchy that distinguishes between market participant assumptions based on market data obtained from sources independent of the reporting entity and the reporting entity’s own assumptions about market participant assumptions. This hierarchy consists of three broad levels: Level 1 - quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date; Level 2 - inputs other than quoted prices included within Level 1, that are observable for the asset or liability, either directly or indirectly; and Level 3 - unobservable inputs for the asset or liability that are used when little or no market data is available. We follow this hierarchy for our assets and liabilities measured at fair value on a recurring and nonrecurring basis. In instances in which the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level of input that is significant to the fair value measurement in its entirety. Our assessment of the significance of the particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. We determine other than temporary impairment in real estate investments and debt and preferred equity investments, including intangibles primarily utilizing cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. As of March 31, 2018, we held notes receivable with an outstanding principal balance of $250.5 million and an accrued interest balance of $7.7 million, which were purchased at par, and were in maturity default at the time of acquisition. In August 2017, the Company determined that it was probable that the loans would not be repaid in full and therefore, the loans were put on non-accrual status. The Company has initiated proceedings to foreclose on the property, and expects to take control of the property unless the buyer is able to repay the principal and interest, including default interest and fees, on the notes receivable in full prior to the completion of the foreclosure process. We believe the collateral value is sufficient to recover the carrying amounts of the notes receivable. In January 2018, the partnership agreement for our investment in 919 Third Avenue was modified resulting in the Company no longer having a controlling interest in this investment. As a result the investment was deconsolidated as of January 1, 2018. The Company recorded its non-controlling interest at fair value resulting in a $49.3 million fair value adjustment in the consolidated statement of operations. This fair value was determined using a third party valuation which primarily utilized cash flow projections that apply, among other things, estimated revenue and expense growth rates, discount rates and capitalization rates, as well as sales comparison approach, which utilizes comparable sales, listings and sales contracts. All of which are classified as Level 3 inputs. Marketable securities classified as Level 1 are derived from quoted prices in active markets. The valuation technique used to measure the fair value of marketable securities classified as Level 2 were valued based on quoted market prices or model driven valuations using the significant inputs derived from or corroborated by observable market data. Marketable securities in an unrealized loss position are not considered to be other than temporarily impaired. We do not intend to sell these securities and it is not more likely than not that we will be required to sell the investments before recovery of their amortized cost bases. The fair value of derivative instruments is based on current market data received from financial sources that trade such instruments and are based on prevailing market data and derived from third party proprietary models based on well-recognized financial principles and reasonable estimates about relevant future market conditions, which are classified as Level 2 inputs. The financial assets and liabilities that are not measured at fair value on our consolidated balance sheets include cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued expenses, debt and preferred equity investments, mortgages and other loans payable and other secured and unsecured debt. The carrying amount of cash and cash equivalents, restricted cash, accounts receivable, and accounts payable and accrued expenses reported in our consolidated balance sheets approximates fair value due to the short term nature of these instruments. The fair value of debt and preferred equity investments, which is classified as Level 3, is estimated by discounting the future cash flows using current interest rates at which similar loans with the same maturities would be made to borrowers with similar credit ratings. The fair value of borrowings, which is classified as Level 3, is estimated by discounting the contractual cash flows of each debt instrument to their present value using adjusted market interest rates, which is provided by a third-party specialist.
Investment in Marketable Securities	Investment in Marketable Securities At acquisition, we designate a debt security as held-to-maturity, available-for-sale, or trading. As of March 31, 2018, we did not have any debt securities designated as held-to-maturity or trading. We account for our available-for-sale debt securities at fair value pursuant to Accounting Standards Codification, or ASC, 820-10, with the net unrealized gains or losses reported as a component of accumulated other comprehensive income or loss. Any unrealized losses that are determined to be other-than-temporary are recognized in earnings up to their credit component. The Company adopted ASU 2016-01 effective January 1, 2018 which required entities to measure investments in equity securities at fair value and recognize any changes in fair value in net income. Upon adoption we did not hold investments in equity securities and therefore did not record a cumulative-effect adjustment. We did not hold investments in equity securities as of March 31, 2018. The cost of bonds and marketable securities sold is determined using the specific identification method.
Investments in Unconsolidated Joint Ventures	Investments in Unconsolidated Joint Ventures We assess our investments in unconsolidated joint ventures for recoverability and if it is determined that a loss in value of the investment is other than temporary, we write down the investment to its fair value. We evaluate our equity investments for impairment based on the joint ventures' projected discounted cash flows.
Reserve for Possible Credit Losses	Reserve for Possible Credit Losses The reserve for possible credit losses in connection with debt and preferred equity investments is the charge to earnings to increase the allowance for possible credit losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. Other factors considered include geographic trends, product diversification, the size of the portfolio and current economic conditions. Based upon these factors, we establish a provision for possible credit loss on each individual investment. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired. Where impairment is indicated on an investment that is held to maturity, a valuation allowance is measured based upon the excess of the recorded investment amount over the fair value of the collateral. Any deficiency between the carrying amount of an asset and the calculated value of the collateral is charged to expense. We continue to assess or adjust our estimates based on circumstances of a loan and the underlying collateral. If additional information reflects increased recovery of our investment, we will adjust our reserves accordingly. There were no loan reserves recorded during the three months ended March 31, 2018 and 2017. Debt and preferred equity investments held for sale are carried at the lower of cost or fair market value using available market information obtained through consultation with dealers or other originators of such investments as well as discounted cash flow models based on Level 3 data pursuant to ASC 820-10. As circumstances change, management may conclude not to sell an investment designated as held for sale. In such situations, the investment will be reclassified at its net carrying value to debt and preferred equity investments held to maturity. For these reclassified investments, the difference between the current carrying value and the expected cash to be collected at maturity will be accreted into income over the remaining term of the investment.
Income Taxes	Income Taxes SL Green is taxed as a REIT under Section 856(c) of the Code. As a REIT, SL Green generally is not subject to Federal income tax. To maintain its qualification as a REIT, SL Green must distribute at least 90% of its REIT taxable income to its stockholders and meet certain other requirements. If SL Green fails to qualify as a REIT in any taxable year, SL Green will be subject to Federal income tax on its taxable income at regular corporate rates. SL Green may also be subject to certain state, local and franchise taxes. Under certain circumstances, Federal income and excise taxes may be due on its undistributed taxable income. The Operating Partnership is a partnership and, as a result, all income and losses of the partnership are allocated to the partners for inclusion in their respective income tax returns. The only provision for income taxes included in the consolidated statements of operations relates to the Operating Partnership’s consolidated taxable REIT subsidiaries. The Operating Partnership may also be subject to certain state, local and franchise taxes. Pursuant to amendments to the Code that became effective January 1, 2001, we have elected, and may elect in the future, to treat certain of our existing or newly created corporate subsidiaries as taxable REIT subsidiaries, or TRSs. In general, TRSs may perform non-customary services for the tenants of the Company, hold assets that we cannot hold directly and generally may engage in any real estate or non-real estate related business. The TRSs generate income, resulting in Federal and state income tax liability for these entities. During the three months ended March 31, 2018, we recorded Federal, state and local tax provisions of $0.5 million. We follow a two-step approach for evaluating uncertain tax positions. Recognition (step one) occurs when an enterprise concludes that a tax position, based solely on its technical merits, is more-likely-than-not to be sustained upon examination. Measurement (step two) determines the amount of benefit that is more-likely-than-not to be realized upon settlement. Derecognition of a tax position that was previously recognized would occur when a company subsequently determines that a tax position no longer meets the more-likely-than-not threshold of being sustained. The use of a valuation allowance as a substitute for derecognition of tax positions is prohibited.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash investments, debt and preferred equity investments and accounts receivable. We place our cash investments with high quality financial institutions. The collateral securing our debt and preferred equity investments is located in the New York metropolitan area. See Note 5, "Debt and Preferred Equity Investments." We perform ongoing credit evaluations of our tenants and require most tenants to provide security deposits or letters of credit. Though these security deposits and letters of credit are insufficient to meet the total value of a tenant's lease obligation, they are a measure of good faith and a source of funds to offset the economic costs associated with lost revenue and the costs associated with re-tenanting a space.
Reclassification	Reclassification Certain prior year balances have been reclassified to conform to our current year presentation.
Accounting Standards Updates	Accounting Standards Updates In February 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-03, Technical Corrections and Improvements to Financial Instruments- Overall (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. These amendments provide additional guidance related to equity securities without a readily determinable fair value, forward contracts and options purchased on those equity securities and fair value option liabilities. The guidance will be effective for the Company in the interim period beginning after June 15, 2018. The Company has not yet adopted this new guidance and does not expect it to have a material impact on the Company’s consolidated financial statements when the new standard is implemented. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities. The amendments in the new standard will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standard will also enhance the presentation of hedge results in the financial statements. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company has not yet adopted the guidance, and does not expect a material impact on the Company’s consolidated financial statements when the new standard is implemented. In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation (Topic 718), Scope of Modification Accounting. The guidance clarifies the changes to the terms or conditions of a share-based payment award that require an entity to apply modification accounting in Topic 718. The Company adopted the guidance on January 1, 2018 and it had no impact on the Company's consolidated financial statements. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash. The guidance requires that the statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash. As a result, entities will no longer present transfers between these items on the statement of cash flows. The Company adopted the guidance on January 1, 2018 and has included the changes in restricted cash when reconciling the beginning-of-period and end-of-period total amounts on the statement of cash flows. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current ‘incurred loss’ model with an ‘expected loss’ approach. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted after December 15, 2018. The Company has not yet adopted this new guidance and is currently evaluating the impact of adopting this new accounting standard on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases. The guidance requires lessees to recognize lease assets and lease liabilities for those leases classified as operating leases under the previous standard. Depending on the lease classification, lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The accounting applied by a lessor is largely unchanged from that applied under the previous standard. However, the presentation and disclosure in the financial statements of non-lease components such as charges to tenants for a building’s operating expenses has been updated. In January 2018, the FASB issued an exposure draft, Leases (Topic 842) Targeted Improvements, which would provide lessors with a practical expedient to not separate non-lease components from the related lease component under certain conditions. At the March 2018 Board meeting, the Board approved an amendment to the practical expedient. We anticipate the majority of our leases would qualify for the amended practical expedient. We expect this amended guidance to be finalized in 2018 and, as a result, we would adopt the practical expedient. Another impact is the measurement and presentation of ground leases under which the Company is lessee. The Company is required to record a liability for the obligation to make payments under the lease and an asset for the right to use the underlying asset during the lease term and will also apply the new expense recognition requirements given the lease classification. The Company is currently quantifying these impacts. The guidance is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company expects to adopt this guidance January 1, 2019 and will apply the modified retrospective approach. In January 2016, the FASB issued ASU 2016-01 (Subtopic 825-10), Recognition and Measurement of Financial Assets and Financial Liabilities. The guidance requires entities to measure equity investments that do not result in consolidation and are not accounted for under the equity method at fair value through earnings, to record changes in instrument-specific credit risk for financial liabilities measured under the fair value option in other comprehensive income, use the exit price notion when measuring an instrument’s fair value for disclosure and to separately present financial assets and liabilities by measurement category and form of instrument on the balance sheet or in the notes to the financial statements. The Company adopted the guidance effective January 1, 2018, and it had no impact on the Company’s consolidated financial statements. In May 2014, the FASB issued a new comprehensive revenue recognition guidance which requires us to recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods and services (ASU 2014-09). The FASB also issued implementation guidance in March 2016, April 2016 and May 2016 - ASU’s 2016-08, 2016-10 and 2016-12, respectively. The Company adopted this guidance on January 1, 2018. Since the Company’s revenue is related to leasing activities, the adoption of this guidance did not have a material impact on the consolidated financial statements. The new guidance is applicable to service contracts with joint ventures for which the Company earns property management fees, leasing commissions and development and construction fees. The adoption of this new guidance did not change the accounting for these fees as the pattern of recognition of revenue does not change with the new guidance. We will continue to recognize revenue over time on these contracts because the customer simultaneously receives and consumes the benefits provided by our performance. In February 2017, the FASB issued ASU No. 2017-05 to clarify the scope of asset derecognition guidance in Subtopic 610-20, which also provided guidance on accounting for partial sales of nonfinancial assets. Subtopic 610-20 was issued in May 2014 as part of ASU 2014-09. The Company adopted this guidance on January 1, 2018, and applied the modified retrospective approach. The Company elected to adopt the practical expedient under ASC 606, Revenue from Contracts with Customers, which allows an entity to apply the guidance only to contracts with non-customers that are open based on ASU 360-20, Real Estate Sales, (i.e. failed sales) as of the adoption date. The Company had one open contract in 2017 with a non-customer that was evaluated under ASC 610-20. The Company entered into an agreement to sell a portion of their interest in an entity that held a controlling interest in the property at 1515 Broadway. Upon execution of the agreement in 2017, the transaction was evaluated under ASC 360-20, Real Estate Sales, and did not meet the criteria for sale accounting. Upon adoption of ASC 606, this contract met the criteria for sale accounting under ASC 610-20. Through the sale, the Company no longer retains a controlling interest, as defined in ASC 810, Consolidation, and the impact of this adjustment is a gain of $0.6 billion from the sale of the partial interest and related step-up in basis to fair value of the non-controlling interest retained. This was recorded in the first quarter of 2018 as an adjustment to beginning retained earnings.

Organization and Basis of Presentation (Tables)

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of commercial office properties



		Consolidated			Unconsolidated		Total
Location	Property Type	Number of Properties		Approximate Square Feet (unaudited)	Number of Properties	Approximate Square Feet (unaudited)	Number of Properties	Approximate Square Feet (unaudited)	Weighted Average Occupancy(1) (unaudited)
Commercial:
Manhattan	Office	20		12,387,091	11	12,165,164	31	24,552,255	94.2	%
	Retail	4	(2)	302,583	9	347,970	13	650,553	94.2	%
	Development/Redevelopment	8		318,985	3	416,214	11	735,199	44.4	%
	Fee Interest	1		176,530	1	—	2	176,530	100.0	%
		33		13,185,189	24	12,929,348	57	26,114,537	92.8	%
Suburban	Office	20	(3)	3,013,200	2	640,000	22	3,653,200	83.1	%
	Retail	1		52,000	—	—	1	52,000	100.0	%
	Development/Redevelopment	1		1,000	1	—	2	1,000	—	%
		22		3,066,200	3	640,000	25	3,706,200	83.3	%
Total commercial properties		55		16,251,389	27	13,569,348	82	29,820,737	91.6	%
Residential:
Manhattan	Residential	3	(2)	472,105	10	2,156,751	13	2,628,856	88.9	%
Suburban	Residential	—		—	—	—	—	—	—	%
Total residential properties		3		472,105	10	2,156,751	13	2,628,856	88.9	%
Total portfolio		58		16,723,494	37	15,726,099	95	32,449,593	91.4	%


(1)	The weighted average occupancy for commercial properties represents the total occupied square feet divided by total square footage at acquisition. The weighted average occupancy for residential properties represents the total occupied units divided by total available units.

(2)


(3)	Includes the properties at 115-117 Stevens Avenue in Valhalla, New York, and 1-6 International Drive in Rye Brook, New York which are classified as held for sale at March 31, 2018.

Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases)



	March 31, 2018			December 31, 2017
Identified intangible assets (included in other assets):
Gross amount	$	282,288		$	325,880
Accumulated amortization	(241,043		)	(277,038		)
Net⁽¹⁾	$	41,245		$	48,842
Identified intangible liabilities (included in deferred revenue):
Gross amount	$	359,469		$	540,283
Accumulated amortization	(256,685		)	(402,583		)
Net⁽¹⁾	$	102,784		$	137,700


(1)	As of March 31, 2018 and December 31, 2017, $0.1 million and $13.9 million, respectively and $0.1 million and $4.1 million, respectively, of net intangible assets and net intangible liabilities, were reclassified to assets held for sale and liabilities related to assets held for sale.

Schedule of marketable securities

At March 31, 2018 and December 31, 2017, we held the following marketable securities (in thousands):



	March 31, 2018		December 31, 2017
Commercial mortgage-backed securities	$	28,252	$	28,579
Total marketable securities available-for-sale	$	28,252	$	28,579

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Properties Held for Sale and Property Dispositions (Tables)

3 Months Ended

Mar. 31, 2018

Discontinued Operations and Disposal Groups [Abstract]

Summary of properties sold

The following table summarizes the properties sold during the three months ended March 31, 2018:

Property

Disposition Date

Property Type

Approximate Square Feet

Sales Price⁽¹⁾

(in millions)

Gain

(in millions)

600 Lexington Avenue⁽²⁾

January 2018

Fee Interest

303,515

305.0

23.8


(1)	Sales price represents the gross sales price for a property or the gross asset valuation for interests in a property.


(2)	Gain on sale amounts do not include adjustments for expenses recorded in subsequent periods.

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=84176398&loc=SL51724579-110230

Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 205
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721675-107760

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721677-107760

+ Details

Debt and Preferred Equity Investments (Tables)

3 Months Ended

Mar. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of debt and preferred equity book balance roll forward



	March 31, 2018			December 31, 2017
Balance at beginning of period ⁽¹⁾	$	2,114,041		$	1,640,412
Debt investment originations/accretion ⁽²⁾	233,370			1,142,591
Preferred equity investment originations/accretion ⁽²⁾	2,074			144,456
Redemptions/sales/syndications/amortization ⁽³⁾	(263,614		)	(813,418		)
Balance at end of period ⁽¹⁾	$	2,085,871		$	2,114,041


(1)	Net of unamortized fees, discounts, and premiums.


(2)	Accretion includes amortization of fees and discounts and paid-in-kind investment income.


(3)	Certain participations in debt investments that were sold or syndicated did not meet the conditions for sale accounting are included in other assets and other liabilities on the consolidated balance sheets.

Summary of debt investments



Loan Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Fixed Rate Investments:
Mortgage/Jr. Mortgage Loan⁽³⁾	$	—	$	—	$	250,464	$	250,464	April 2017
Mortgage Loan⁽⁴⁾	—		—		26,380		26,366		February 2019
Mortgage Loan	—		—		201		239		August 2019
Mezzanine Loan^(5a)	—		1,160,000		206,230		204,005		March 2020
Mezzanine Loan	—		15,000		3,500		3,500		September 2021
Mezzanine Loan	—		147,000		24,918		24,913		April 2022
Mezzanine Loan	—		280,000		35,074		34,600		August 2022
Mezzanine Loan	—		86,580		12,701		12,699		November 2023
Mezzanine Loan^(5b)	—		115,000		12,934		12,932		June 2024
Mezzanine Loan	—		95,000		30,000		30,000		January 2025
Mezzanine Loan	—		340,000		15,000		15,000		November 2026
Mezzanine Loan	—		1,657,500		55,250		55,250		June 2027
Total fixed rate	$	—	$	3,896,080	$	672,652	$	669,968
Floating Rate Investments:
Mezzanine Loan⁽⁶⁾	—		40,000		19,999		19,982		April 2018



Loan Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Mezzanine Loan⁽⁶⁾	—		75,014		23,346		34,947		April 2018
Mezzanine Loan	523		20,523		10,952		10,934		August 2018
Mortgage/Mezzanine Loan	—		—		19,965		19,940		August 2018
Mezzanine Loan	—		65,000		14,973		14,955		August 2018
Mortgage/Mezzanine Loan	—		—		16,980		16,969		September 2018
Mezzanine Loan	—		37,500		14,908		14,855		September 2018
Mortgage/Mezzanine Loan	391		—		23,609		23,609		October 2018
Mezzanine Loan	2,325		45,025		34,975		34,879		October 2018
Mezzanine Loan^(5c)	—		85,000		15,327		15,381		December 2018
Mezzanine Loan^(5d)	—		65,000		14,816		14,869		December 2018
Mezzanine Loan	—		33,000		26,947		26,927		December 2018
Mezzanine Loan	—		175,000		59,797		59,723		December 2018
Mezzanine Loan	—		45,000		12,192		12,174		January 2019
Mezzanine Loan	4,493		27,852		9,457		8,550		January 2019
Mezzanine Loan^(5e)(7)	795		—		15,150		15,148		March 2019
Mezzanine Loan	—		38,000		21,951		21,939		March 2019
Mezzanine Loan	—		175,000		37,307		37,250		April 2019
Mezzanine Loan	—		265,000		24,862		24,830		April 2019
Mortgage/Jr. Mortgage Participation Loan	24,587		208,094		74,944		71,832		August 2019
Mezzanine Loan	2,034		189,829		37,867		37,851		September 2019
Mortgage/Mezzanine Loan	22,570		—		146,517		143,919		September 2019
Mezzanine Loan	—		350,000		34,773		34,737		October 2019
Mortgage/Mezzanine Loan	1,792		—		66,026		—		December 2019
Mortgage/Mezzanine Loan	21,303		—		48,245		43,845		January 2020
Mezzanine Loan	1,592		568,461		77,927		75,834		January 2020
Mortgage Loan	16,038		—		83,465		—		February 2020
Mezzanine Loan	5,993		294,036		48,490		—		March 2020
Mezzanine Loan	6,654		35,112		11,539		11,259		July 2020
Mezzanine Loan	47,557		326,552		79,477		75,428		November 2020
Mortgage and Mezzanine Loan	40,798		—		90,789		88,989		December 2020
Mortgage and Mezzanine Loan	—		—		35,179		35,152		December 2020
Jr. Mortgage Participation/Mezzanine Loan	—		60,000		15,642		15,635		July 2021
Mortgage/Mezzanine Loan⁽⁸⁾	—		—		—		162,553		—
Mezzanine Loan⁽⁸⁾	—		—		—		74,755		—
Total floating rate	$	199,445	$	3,223,998	$	1,268,393	$	1,299,650
Total	$	199,445	$	7,120,078	$	1,941,045	$	1,969,618


(1)	Carrying value is net of discounts, premiums, original issue discounts and deferred origination fees.


(2)	Represents contractual maturity, excluding any unexercised extension options.

(3)


(4)	In September 2014, we acquired a $26.4 million mortgage loan at a $0.2 million discount and a $5.7 million junior mortgage participation at a $5.7 million discount. The junior mortgage participation was a nonperforming loan at acquisition, is currently on non-accrual status and has no carrying value.


(5)	Carrying value is net of the following amounts that were sold or syndicated, which are included in other assets and other liabilities on the consolidated balance sheets as a result of the transfers not meeting the conditions for sale accounting: (a) $1.3 million, (b) $12.0 million, (c) $14.6 million, (d) $14.1 million, and (e) $5.1 million.


(6)	This loan was extended in April 2018.


(7)	This loan was extended in March 2018.


(8)	This loan was repaid in February 2018.

Summary of preferred equity investments

As of March 31, 2018 and December 31, 2017, we held the following preferred equity investments with an aggregate weighted average current yield of 6.97% at March 31, 2018 (in thousands):



Type	March 31, 2018 Future Funding Obligations		March 31, 2018 Senior Financing		March 31, 2018 Carrying Value ⁽¹⁾		December 31, 2017 Carrying Value ⁽¹⁾		Maturity Date ⁽²⁾
Preferred Equity	$	—	$	272,000	$	144,826	$	144,423	April 2021
Total	$	—	$	272,000	$	144,826	$	144,423


(1)	Carrying value is net of deferred origination fees.


(2)	Represents contractual maturity, excluding any unexercised extension options.

Investments in Unconsolidated Joint Ventures (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of Equity Method Investments [Line Items]

Schedule of general information on joint ventures

The table below provides general information on each of our joint ventures as of March 31, 2018:



Property	Partner	Ownership Interest⁽¹⁾	Economic Interest⁽¹⁾	Unaudited Approximate Square Feet	Acquisition Date⁽²⁾	Acquisition Price⁽²⁾(in thousands)
100 Park Avenue	Prudential Real Estate Investors	49.90%	49.90%	834,000	February 2000	$	95,800
717 Fifth Avenue	Jeff Sutton/Private Investor	10.92%	10.92%	119,500	September 2006	251,900
800 Third Avenue	Private Investors	60.52%	60.52%	526,000	December 2006	285,000
919 Third Avenue⁽³⁾	New York State Teacher's Retirement System	51.00%	51.00%	1,454,000	January 2007	1,256,727
1745 Broadway⁽⁴⁾	Ivanhoe Cambridge, Inc.	56.87%	56.87%	674,000	April 2007	520,000
Jericho Plaza⁽⁵⁾	Onyx Equities/Credit Suisse	11.67%	11.67%	640,000	April 2007	210,000
11 West 34th Street	Private Investor/ Jeff Sutton	30.00%	30.00%	17,150	December 2010	10,800
3 Columbus Circle⁽⁶⁾	The Moinian Group	48.90%	48.90%	741,500	January 2011	500,000
280 Park Avenue	Vornado Realty Trust	50.00%	50.00%	1,219,158	March 2011	400,000
1552-1560 Broadway⁽⁷⁾	Jeff Sutton	50.00%	50.00%	57,718	August 2011	136,550
724 Fifth Avenue	Jeff Sutton	50.00%	50.00%	65,010	January 2012	223,000
10 East 53rd Street	Canadian Pension Plan Investment Board	55.00%	55.00%	354,300	February 2012	252,500
521 Fifth Avenue	Plaza Global Real Estate Partners LP	50.50%	50.50%	460,000	November 2012	315,000
21 East 66th Street⁽⁸⁾	Private Investors	32.28%	32.28%	13,069	December 2012	75,000
650 Fifth Avenue⁽⁹⁾	Jeff Sutton	50.00%	50.00%	69,214	November 2013	—
121 Greene Street	Jeff Sutton	50.00%	50.00%	7,131	September 2014	27,400
175-225 Third Street Brooklyn, New York⁽¹⁰⁾	KCLW 3rd Street LLC/LIVWRK LLC	95.00%	95.00%	—	October 2014	74,600
55 West 46th Street	Prudential Real Estate Investors	25.00%	25.00%	347,000	November 2014	295,000
Stonehenge Portfolio⁽¹¹⁾	Various	Various	Various	1,439,016	February 2015	36,668
131-137 Spring Street	Invesco Real Estate	20.00%	20.00%	68,342	August 2015	277,750
605 West 42nd Street	The Moinian Group	20.00%	20.00%	927,358	April 2016	759,000
11 Madison Avenue	PGIM Real Estate	60.00%	60.00%	2,314,000	August 2016	2,605,000
333 East 22nd Street	Private Investors	33.33%	33.33%	26,926	August 2016	—
400 E 57th Street⁽¹²⁾	BlackRock, Inc and Stonehenge Partners	51.00%	41.00%	290,482	October 2016	170,000
One Vanderbilt⁽¹³⁾	National Pension Service of Korea/Hines Interest LP	71.01%	71.01%	—	January 2017	3,310,000
Mezzanine Loan⁽¹⁴⁾	Private Investors	33.33%	33.33%	—	May 2017	15,000
Worldwide Plaza	RXR Realty / New York REIT / Private Investor	24.35%	24.35%	2,048,725	October 2017	1,725,000
1515 Broadway⁽¹⁵⁾	Allianz Real Estate of America	56.87%	56.87%	1,750,000	November 2017	1,950,000


(1)	Ownership interest and economic interest represent the Company's interests in the joint venture as of March 31, 2018. Changes in ownership or economic interests within the current year are disclosed in the notes below.


(2)	Acquisition date and price represent the date on which the Company initially acquired an interest in the joint venture and the actual or implied gross purchase price for the joint venture on that date. Acquisition date and price are not adjusted for subsequent acquisitions or dispositions of interest.

(3)


(4)	In April 2018, the Company entered into an agreement to sell its interest in 1745 Broadway. The transaction is expected to close in the second quarter of 2018.


(5)	In April 2018, the Company entered into an agreement to sell its interest in Jericho Plaza. The transaction is expected to close in the second quarter of 2018.


(6)	As a result of the sale of a condominium interest in September 2012, Young & Rubicam, Inc., or Y&R, owns floors three through eight at the property. Because the joint venture has an option to repurchase these floors, the gain associated with this sale was deferred.


(7)	The purchase price represents only the purchase of the 1552 Broadway interest which comprised approximately 13,045 square feet. The joint venture also owns a long-term leasehold interest in the retail space and certain other spaces at 1560 Broadway, which is adjacent to 1552 Broadway.


(8)	We hold a 32.28% interest in three retail and two residential units at the property and a 16.14% interest in three residential units at the property.

(9)


(10)	In April 2018, the Company, together with its joint venture partners, closed on the sale of this property.


(11)	In February and March 2018, the Company, together with its joint venture partner, closed on the sale of two properties from the Stonehenge Portfolio. These sales are further described under Sale of Joint Venture Interest of Properties below.

(12)


(13)	The partners have committed aggregate equity totaling no less than $525 million and their ownership interest in the joint venture is based on their capital contributions, up to an aggregate maximum of 29.0%. At March 31, 2018 the total of the two partners' ownership interests based on equity contributed was 6.84%.

(14)

(15)

As of March 31, 2018 and December 31, 2017, the carrying value for acquisition, development and construction arrangements were as follows (in thousands):



Loan Type	March 31, 2018		December 31, 2017		Maturity Date
Mezzanine Loan⁽¹⁾	$	44,751	$	44,823	February 2022
Mezzanine Loan⁽²⁾	27,628		26,716		July 2036
Mezzanine Loan and Preferred Equity⁽³⁾	—		100,000
	$	72,379	$	171,539


(1)	We have an option to convert our loan to an equity interest subject to certain conditions. We have determined that our option to convert the loan to equity is not a derivative financial instrument pursuant to GAAP.


(2)	The Company has the ability to convert this loan into an equity position starting in 2021 and the borrower is able to force this conversion in 2024.


(3)	The mezzanine loan was repaid and the preferred equity interest was redeemed in March 2018.

Schedule of first mortgage notes payable collateralized by the respective joint venture properties and assignment of leases

The first mortgage notes and other loans payable collateralized by the respective joint venture properties and assignment of leases at March 31, 2018 and December 31, 2017, respectively, are as follows (amounts in thousands):



Property	Economic Interest ⁽¹⁾		Maturity Date	Interest Rate ⁽²⁾			March 31, 2018			December 31, 2017
Fixed Rate Debt:
521 Fifth Avenue	50.50	%	November 2019		3.73	%	$	170,000		$	170,000
717 Fifth Avenue ⁽³⁾	10.92	%	July 2022		4.45	%	300,000			300,000
717 Fifth Avenue ⁽³⁾	10.92	%	July 2022		5.50	%	355,328			355,328
650 Fifth Avenue ⁽⁴⁾	50.00	%	October 2022		4.46	%	210,000			210,000
650 Fifth Avenue ⁽⁴⁾	50.00	%	October 2022		5.45	%	65,000			65,000
21 East 66th Street	32.28	%	April 2023		3.60	%	12,000			12,000
919 Third Avenue	51.00	%	June 2023		5.12	%	500,000			—
3 Columbus Circle	48.90	%	March 2025		3.61	%	350,000			350,000
1515 Broadway	56.87	%	March 2025		3.93	%	868,309			872,528
11 Madison Avenue	60.00	%	September 2025		3.84	%	1,400,000			1,400,000
800 Third Avenue	60.52	%	February 2026		3.37	%	177,000			177,000
400 East 57th Street	41.00	%	November 2026		3.00	%	100,000			100,000
Worldwide Plaza	24.35	%	November 2027		3.98	%	1,200,000			1,200,000
Stonehenge Portfolio ⁽⁵⁾	Various		Various		4.25	%	306,990			357,282
Total fixed rate debt							$	6,014,627		$	5,569,138
Floating Rate Debt:
175-225 Third Street ⁽⁶⁾	95.00	%	June 2018	Prime+	1.00	%	$	40,000		$	40,000
Jericho Plaza ⁽⁷⁾	11.67	%	March 2019	L+	4.15	%	81,922			81,099
724 Fifth Avenue ⁽⁸⁾	50.00	%	April 2019	L+	2.42	%	275,000			275,000
280 Park Avenue	50.00	%	September 2019	L+	1.73	%	1,200,000			1,200,000
121 Greene Street	50.00	%	November 2019	L+	1.50	%	15,000			15,000
1745 Broadway ⁽⁹⁾	56.87	%	January 2020	L+	1.85	%	345,000			345,000
10 East 53rd Street	55.00	%	February 2020	L+	2.25	%	170,000			170,000
131-137 Spring Street	20.00	%	August 2020	L+	1.55	%	141,000			141,000
1552 Broadway	50.00	%	October 2020	L+	2.65	%	195,000			195,000
55 West 46th Street ⁽¹⁰⁾	25.00	%	November 2020	L+	2.13	%	172,511			171,444
11 West 34th Street	30.00	%	January 2021	L+	1.45	%	23,000			23,000
100 Park Avenue	49.90	%	February 2021	L+	1.75	%	360,000			360,000
One Vanderbilt ⁽¹¹⁾	71.01	%	September 2021	L+	3.50	%	375,000			355,535
605 West 42nd Street	20.00	%	August 2027	L+	1.44	%	550,000			550,000
21 East 66th Street	32.28	%	June 2033	1 Year Treasury+	2.75	%	1,628			1,648
Stonehenge Portfolio	Various		January 2021	L+	1.40	%	38,000			55,340
Total floating rate debt							$	3,983,061		$	3,979,066
Total joint venture mortgages and other loans payable							$	9,997,688		$	9,548,204
Deferred financing costs, net							(120,809		)	(136,103		)
Total joint venture mortgages and other loans payable, net							$	9,876,879		$	9,412,101


(1)	Economic interest represents the Company's interests in the joint venture as of March 31, 2018. Changes in ownership or economic interests, if any, within the current year are disclosed in the notes to the investment in unconsolidated joint ventures table above.


(2)	Interest rates as of March 31, 2018, taking into account interest rate hedges in effect during the period. Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.


(3)	These loans are comprised of a $300.0 million fixed rate mortgage loan and $355.3 million mezzanine loan. The mezzanine loan is subject to accretion based on the difference between contractual interest rate and contractual pay rate.


(4)	These loans are comprised of a $210.0 million fixed rate mortgage loan and $65.0 million fixed rate mezzanine loan.


(5)	Amount is comprised of $136.4 million and $170.6 million in fixed-rate mortgages that mature in August 2019 and June 2024, respectively.


(6)	In April 2018, along with our joint venture partner, we closed on the sale of the property.


(7)	The property secures a two year $100.0 million loan, of which $81.9 million is currently outstanding. In March 2018, we exercised a 12-month extension option.


(8)	In April 2018, we exercised a 12-month extension option.


(9)	This loan has a committed amount of $375.0 million, of which $30.0 million was unfunded as of March 31, 2018.


(10)	This loan has a committed amount of $195.0 million, of which $22.5 million was unfunded as of March 31, 2018.


(11)	This loan is a $1.5 billion construction facility, which bears interest at 350 basis points over 30-day LIBOR, with reductions based on meeting certain conditions, and has an initial five-year term with two one-year extension options. Advances under the loan are subject to incurred costs, funded equity, loan to value thresholds, and entering into construction contracts.

Schedule of combined balance sheets for the unconsolidated joint ventures

The combined balance sheets for the unconsolidated joint ventures, at March 31, 2018 and December 31, 2017 are as follows (in thousands):



	March 31, 2018		December 31, 2017
Assets ⁽¹⁾
Commercial real estate property, net	$	14,652,483	$	12,822,133
Cash and restricted cash	452,648		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	359,396		349,944
Debt and preferred equity investments, net	103,379		202,539
Other assets	2,361,367		1,407,806
Total assets	$	17,929,273	$	15,277,331
Liabilities and equity ⁽¹⁾
Mortgages and other loans payable, net	$	9,876,879	$	9,412,101
Deferred revenue/gain	1,911,564		985,648
Other liabilities	493,369		411,053
Members' equity	5,647,461		4,468,529
Total liabilities and members' equity	$	17,929,273	$	15,277,331
Company's investments in unconsolidated joint ventures	$	3,034,596	$	2,362,989


(1)	The combined assets, liabilities and equity for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.

Schedule of combined statements of income for the unconsolidated joint ventures

The combined statements of operations for the unconsolidated joint ventures, for the three months ended March 31, 2018 and 2017, are as follows (in thousands):



	Three Months Ended March 31,
	2018			2017
Total revenues	$	320,941		$	216,521
Operating expenses	59,773			38,794
Ground rent	4,393			4,251
Real estate taxes	57,027			34,939
Interest expense, net of interest income	89,741			55,328
Amortization of deferred financing costs	5,116			6,505
Transaction related costs	—			89
Depreciation and amortization	105,080			71,164
Total expenses	321,130			211,070
Net (loss) income before gain on sale ⁽¹⁾	$	(189	)	$	5,451
Company's equity in net income from unconsolidated joint ventures ⁽¹⁾	$	4,036		$	6,614


(1)	The combined statements of operation and the Company's equity in net income for the unconsolidated joint ventures reflects the effect of step ups in basis on the retained non-controlling interests in deconsolidated investments as a result of the adoption of ASC 610-20 in January 2018.

Discontinued Operations, Disposed of by Sale [Member]

Schedule of Equity Method Investments [Line Items]

Schedule of general information on joint ventures

The following table summarizes the investments in unconsolidated joint ventures sold during the three months ended March 31, 2018:



Property	Ownership Interest	Disposition Date	Type of Sale	Gross Asset Valuation (in thousands)⁽¹⁾		Loss on Sale (in thousands)⁽²⁾
1274 Fifth Avenue⁽³⁾	9.83%	February 2018	Property	$	44,100	$	(362	)
1515 Broadway⁽⁴⁾	13.00%	February 2018	Ownership Interest	1,950,000		—
Stonehenge Village⁽³⁾	5.00%	March 2018	Property	287,000		(5,701		)


(1)	Represents implied gross valuation for the joint venture or sales price of the property.


(2)	Represents the Company's share of the loss.


(3)	Property was part of the Stonehenge Portfolio.


(4)	Our investment in 1515 Broadway was marked to fair value on January 1, 2018 upon adoption of ASC 610-20.

Deferred Costs (Tables)

3 Months Ended

Mar. 31, 2018

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of components of deferred costs

Deferred costs at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018			December 31, 2017
Deferred leasing costs	$	415,824		$	443,341
Less: accumulated amortization	(220,267		)	(217,140		)
Deferred costs, net	$	195,557		$	226,201

Mortgages and Other Loans Payable (Tables)

3 Months Ended

Mar. 31, 2018

Mortgages and Other Loans Payable

Schedule of first mortgages and other loans payable collateralized by the respective properties and assignment of leases



Property	Maturity Date	Interest Rate ⁽¹⁾			March 31, 2018			December 31, 2017
Fixed Rate Debt:
Unsecured Loan	June 2018		4.81	%	$	16,000		$	16,000
One Madison Avenue	May 2020		5.91	%	477,843			486,153
762 Madison Avenue	February 2022		5.00	%	771			771
100 Church Street	July 2022		4.68	%	216,240			217,273
420 Lexington Avenue	October 2024		3.99	%	300,000			300,000
400 East 58th Street ⁽²⁾	November 2026		3.00	%	40,000			40,000
Landmark Square	January 2027		4.90	%	100,000			100,000
485 Lexington Avenue	February 2027		4.25	%	450,000			450,000
1080 Amsterdam ⁽³⁾	February 2027		3.58	%	36,300			36,363
315 West 33rd Street	February 2027		4.17	%	250,000			250,000
Series J Preferred Units ⁽⁴⁾	April 2051		3.75	%	4,000			4,000
919 Third Avenue ⁽⁵⁾					—			500,000
Total fixed rate debt					$	1,891,154		$	2,400,560
Floating Rate Debt:
183, 187 Broadway & 5-7 Dey Street	May 2018	L+	2.70	%	$	58,000		$	58,000
2017 Master Repurchase Agreement	June 2018	L+	2.23	%	189,883			90,809
719 Seventh Avenue	February 2019	L+	3.05	%	42,143			41,622
220 East 42nd Street	October 2020	L+	1.60	%	275,000			275,000
Total floating rate debt					$	565,026		$	465,431
Total fixed rate and floating rate debt					$	2,456,180		$	2,865,991
Mortgages reclassed to liabilities related to assets held for sale					—			—
Total mortgages and other loans payable					$	2,456,180		$	2,865,991
Deferred financing costs, net of amortization					(22,186		)	(28,709		)
Total mortgages and other loans payable, net					$	2,433,994		$	2,837,282


(1)	Interest rate as of March 31, 2018, taking into account interest rate hedges in effect during the period. Floating rate debt is presented with the stated interest rate spread over 30-day LIBOR, unless otherwise specified.


(2)	The loan carries a fixed interest rate of 300 basis points for the first five years and is prepayable without penalty at the end of year five.


(3)	The loan is comprised of a $35.5 million mortgage loan and $0.9 million subordinate loan with a fixed interest rate of 350 basis points and 700 basis points, respectively, for the first five years and is prepayable without penalty at the end of year five.

(4)


(5)	Our investment in the property was deconsolidated as of January 1, 2018. See Note 6, "Investments in Unconsolidated Joint Ventures".

Corporate Indebtedness (Tables)

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Schedule of senior unsecured notes and other related disclosures by scheduled maturity date

The following table sets forth our senior unsecured notes and other related disclosures as of March 31, 2018 and December 31, 2017, respectively, by scheduled maturity date (amounts in thousands):



Issuance	March 31, 2018 Unpaid Principal Balance		March 31, 2018 Accreted Balance			December 31, 2017 Accreted Balance			Coupon Rate ⁽¹⁾		Initial Term (in Years)	Maturity Date
August 5, 2011 ⁽²⁾	$	250,000	$	249,972		$	249,953		5.00	%	7	August 2018
March 16, 2010 ⁽²⁾	250,000		250,000			250,000			7.75	%	10	March 2020
October 5, 2017 ⁽³⁾	500,000		499,514			499,489			3.25	%	5	October 2022
November 15, 2012 ⁽⁴⁾	300,000		304,920			305,163			4.50	%	10	December 2022
December 17, 2015 ⁽²⁾	100,000		100,000			100,000			4.27	%	10	December 2025
	$	1,400,000	$	1,404,406		$	1,404,605
Deferred financing costs, net			(8,086		)	(8,666		)
	$	1,400,000	$	1,396,320		$	1,395,939


(1)	Interest on the senior unsecured notes is payable semi-annually with principal and unpaid interest due on the scheduled maturity dates.


(2)	Issued by the Company, the Operating Partnership and ROP, as co-obligors.


(3)	Issued by the Operating Partnership with the Company and ROP as guarantors.


(4)	In October 2017, the Company, the Operating Partnership and ROP, as co-obligors, issued an additional $100.0 million of 4.50% senior unsecured notes due December 2022. The notes were priced at 105.334%.

Schedule of combined aggregate principal maturities



	Scheduled Amortization		Principal		Revolving Credit Facility		Unsecured Term Loans		Trust Preferred Securities		Senior Unsecured Notes		Total		Joint Venture Debt
Remaining 2018	$	28,555	$	74,000	$	—	$	—	$	—	$	250,000	$	352,555	$	45,477
2019	42,271		42,143		—		—		—		—		84,414		262,460
2020	23,466		869,414		—		—		—		250,000		1,142,880		471,714
2021	11,638		—		—		—		—		—		11,638		454,571
2022	9,430		198,555		—		—		—		800,000		1,007,985		220,759
Thereafter	16,591		1,140,117		—		1,500,000		100,000		100,000		2,856,708		2,878,381
	$	131,951	$	2,324,229	$	—	$	1,500,000	$	100,000	$	1,400,000	$	5,456,180	$	4,333,362

Schedule of consolidated interest expense, excluding capitalized interest

Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands):



	Three Months Ended March 31,
	2018			2017
Interest expense before capitalized interest	$	54,918		$	72,422
Interest capitalized	(6,686		)	(6,279		)
Interest income	(316		)	(521		)
Interest expense, net	$	47,916		$	65,622

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21521-112644

+ Details

Related Party Transactions (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of amounts due from/to related parties

Amounts due from joint ventures and related parties at March 31, 2018 and December 31, 2017 consisted of the following (in thousands):



	March 31, 2018		December 31, 2017
Due from joint ventures	$	21,972	$	15,025
Other	9,333		8,014
Related party receivables	$	31,305	$	23,039

Noncontrolling Interests on the Company's Consolidated Financial Statements (Tables)

3 Months Ended

Mar. 31, 2018

Noncontrolling Interest [Abstract]

Schedule of Noncontrolling Interest



	March 31, 2018			December 31, 2017
Balance at beginning of period	$	461,954		$	473,882
Distributions	(3,841		)	(14,266		)
Issuance of common units	15,448			25,723
Redemption of common units	—			(21,574		)
Net income	5,272			3,995
Accumulated other comprehensive income allocation	619			(94		)
Fair value adjustment	(3,645		)	(5,712		)
Balance at end of period	$	475,807		$	461,954

Schedule of Preferred Unit Activity



	March 31, 2018			December 31, 2017
Balance at beginning of period	$	301,735		$	302,010
Issuance of preferred units	—			—
Redemption of preferred units	(150		)	(275		)
Balance at end of period	$	301,585		$	301,735

Stockholders' Equity of the Company (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Class of Treasury Stock

At March 31, 2018, repurchases under the plan were as follows:



Period	Shares repurchased	Average price paid per share	Cumulative number of shares repurchased as part of the repurchase plan or programs	Maximum approximate dollar value of shares that may yet be repurchased under the plan (in millions)⁽¹⁾
2017	8,342,411	$101.64	8,342,411	$652.0
First quarter 2018 ⁽²⁾	3,653,928	$97.07	11,996,339	$297.2


(1)	Reflective of $1.5 billion plan maximum as of March 31, 2018.


(2)	Includes 142,004 shares of common stock repurchased by the Company in March 2018 that were settled in April 2018.

Schedule of Earnings Per Share

SL Green's earnings per share for the three months ended March 31, 2018 and 2017 are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic Earnings:
Income attributable to SL Green common stockholders	$	101,766	$	11,351
Effect of Dilutive Securities:
Redemption of units to common shares	5,272		476
Diluted Earnings:
Income attributable to SL Green common stockholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic Shares:
Weighted average common stock outstanding	90,520	100,643
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares	4,683	4,607
Stock-based compensation plans	53	304
Diluted weighted average common stock outstanding	95,256	105,554

Partners' Capital of the Operating Partnership (Tables)

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Schedule of calculation of numerator and denominator in earnings per unit

The Operating Partnership's earnings per unit for the three months ended March 31, 2018 and 2017, respectively, are computed as follows (in thousands):



	Three Months Ended March 31,
Numerator	2018		2017
Basic and Diluted Earnings:
Income attributable to SLGOP common unitholders	$	107,038	$	11,827



	Three Months Ended March 31,
Denominator	2018	2017
Basic units:
Weighted average common units outstanding	95,203	105,250
Effect of Dilutive Securities:
Stock-based compensation plans	53	304
Diluted weighted average common units outstanding	95,256	105,554

Share-based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of weighted average assumptions used to estimate the grant date fair value of options granted



	March 31, 2018		December 31, 2017
Dividend yield	2.85	%	2.51	%
Expected life	3.5 years		4.4 years
Risk-free interest rate	2.48	%	1.73	%
Expected stock price volatility	22.00	%	28.10	%

Summary of the status of stock options and changes during the period



	March 31, 2018					December 31, 2017
	Options Outstanding			Weighted Average Exercise Price		Options Outstanding			Weighted Average Exercise Price
Balance at beginning of period	1,548,719			$	101.48	1,737,213			$	98.44
Granted	6,000			97.91		174,000			105.66
Exercised	(4,000		)	88.91		(292,193		)	81.07
Lapsed or canceled	(18,799		)	111.39		(70,301		)	121.68
Balance at end of period	1,531,920			$	101.37	1,548,719			$	101.48
Options exercisable at end of period	1,040,103			$	98.25	800,902			$	94.33
Total fair value of options granted during the period	$	84,068				$	3,816,652

Summary of restricted stock and charges during the period

A summary of the Company's restricted stock as of March 31, 2018 and December 31, 2017 and charges during the three months ended March 31, 2018 and the year ended December 31, 2017, are as follows:



	March 31, 2018			December 31, 2017
Balance at beginning of period	3,298,216			3,202,031
Granted	33,450			96,185
Canceled	(4,550		)	—
Balance at end of period	3,327,116			3,298,216
Vested during the period	91,014			95,736
Compensation expense recorded	$	3,134,975		$	9,809,749
Total fair value of restricted stock granted during the period	$	3,237,006		$	9,905,986

Accumulated Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2018

Equity [Abstract]

Schedule of accumulated other comprehensive income (loss)

The following tables set forth the changes in accumulated other comprehensive income (loss) by component as of March 31, 2018 (in thousands):



	Net unrealized gain on derivative instruments ⁽¹⁾		SL Green’s share of joint venture net unrealized gain on derivative instruments ⁽²⁾		Net unrealized gain on marketable securities			Total
Balance at December 31, 2017	$	12,542	$	5,020	$	1,042		$	18,604
Other comprehensive (loss) income before reclassifications	6,859		3,114		(315		)	9,658
Amounts reclassified from accumulated other comprehensive income	310		1		—			311
Balance at March 31, 2018	$	19,711	$	8,135	$	727		$	28,573

(1)


(2)	Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net income from unconsolidated joint ventures in the respective consolidated statements of operations.

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Fair value measurements, recurring and nonrecurring



	March 31, 2018
	Total		Level 1		Level 2		Level 3
Assets:
Marketable securities	$	28,252	$	—	$	28,252	$	—
Interest rate cap and swap agreements (included in other assets)	$	23,629	$	—	$	23,629	$	—



	December 31, 2017
	Total		Level 1		Level 2		Level 3
Assets:
Marketable securities	$	28,579	$	—	$	28,579	$	—
Interest rate cap and swap agreements (included in other assets)	$	16,692	$	—	$	16,692	$	—

Fair value, by balance sheet grouping

The following table provides the carrying value and fair value of these financial instruments as of March 31, 2018 and December 31, 2017 (in thousands):



	March 31, 2018				December 31, 2017
	Carrying Value⁽¹⁾		Fair Value		Carrying Value⁽¹⁾		Fair Value

Debt and preferred equity investments	$	2,085,871	⁽²⁾		$	2,114,041	⁽²⁾

Fixed rate debt	$	3,795,560	$	3,840,843	$	4,305,165	$	4,421,866
Variable rate debt	1,665,026		1,673,313		1,605,431		1,612,224
	$	5,460,586	$	5,514,156	$	5,910,596	$	6,034,090


(1)	Amounts exclude net deferred financing costs.


(2)	At both March 31, 2018 and December 31, 2017, debt and preferred equity investments had an estimated fair value ranging between $2.1 billion and $2.3 billion.

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Financial Instruments: Derivatives and Hedging (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of notional and fair value of derivative financial instruments and foreign currency hedges



	Notional Value		Strike Rate		Effective Date	Expiration Date	Balance Sheet Location	Fair Value
Interest Rate Swap	$	200,000	1.131	%	July 2016	July 2023	Other Assets	$	14,149
Interest Rate Swap	100,000		1.161	%	July 2016	July 2023	Other Assets	6,927
Interest Rate Cap	137,500		4.000	%	September 2017	September 2019	Other Assets	19
Interest Rate Swap	100,000		1.928	%	December 2017	November 2020	Other Assets	1,273
Interest Rate Swap	100,000		1.934	%	December 2017	November 2020	Other Assets	1,260
								$	23,628

Schedule of effect of derivative financial instruments on consolidated statements of income



	Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion)					Location of (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income	Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)				Location of (Loss) Recognized in Income on Derivative	Amount of (Loss) Recognized into Income (Ineffective Portion)
	Three Months Ended March 31,						Three Months Ended March 31,					Three Months Ended March 31,
Derivative	2018		2017				2018		2017			2018			2017
Interest Rate Swaps/Caps	$	7,282	$	(3,137	)	Interest expense	$	329	$	979	Interest expense	$	(9	)	$	(8	)
Share of unconsolidated joint ventures' derivative instruments	3,313		341			Equity in net income from unconsolidated joint ventures	1		399		Equity in net income from unconsolidated joint ventures	(89		)	(95		)
	$	10,595	$	(2,796	)		$	330	$	1,378		$	(98	)	$	(103	)

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41641-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41678-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41638-113959

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579240-113959

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41620-113959

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum rental payments for operating leases

The following is a schedule of future minimum lease payments under capital leases and non-cancellable operating leases with initial terms in excess of one year as of March 31, 2018 (in thousands):



	Capital lease			Non-cancellable operating leases
Remaining 2018	$	1,790		$	23,286
2019	2,411			31,066
2020	2,620			31,437
2021	2,794			31,628
2022	2,794			29,472
2023	2,794			27,166
Thereafter	817,100			676,088
Total minimum lease payments	$	832,303		$	850,143
Amount representing interest	(789,274		)
Capital lease obligations	$	43,029

Schedule of future minimum rental payments for capital leases

The following is a schedule of future minimum lease payments under capital leases and non-cancellable operating leases with initial terms in excess of one year as of March 31, 2018 (in thousands):



	Capital lease			Non-cancellable operating leases
Remaining 2018	$	1,790		$	23,286
2019	2,411			31,066
2020	2,620			31,437
2021	2,794			31,628
2022	2,794			29,472
2023	2,794			27,166
Thereafter	817,100			676,088
Total minimum lease payments	$	832,303		$	850,143
Amount representing interest	(789,274		)
Capital lease obligations	$	43,029

Segment Information (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Schedule of selected results of operations and selected asset information



	Real Estate Segment		Debt and Preferred Equity Segment		Total Company
Total revenues
Three months ended:
March 31, 2018	$	256,405	$	45,290	$	301,695
March 31, 2017	337,082		40,299		377,381
Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities
Three months ended:
March 31, 2018	$	14,024	$	33,425	$	47,449
March 31, 2017	13,807		37,513		51,320
Total assets
As of:
March 31, 2018	$	11,144,740	$	2,236,130	$	13,380,870
December 31, 2017	11,643,261		2,339,643		13,982,904

Schedule of reconciliation of income from continuing operations to net income attributable to SL Green common stockholders



	Three Months Ended March 31,
	2018			2017
Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities	$	47,449		$	51,320
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440		)	2,047
Purchase price and other fair value adjustments	49,293			—
Gain on sale of real estate, net	23,521			567
Depreciable real estate reserves	—			(56,272		)
Gain on sale of investment in marketable securities	—			3,262
Net income	$	113,823		$	924

Organization and Basis of Presentation - Additional Information (Details) - SL Green Operating Partnership	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%
Noncontrolling interest in the operating partnership (as a percent)	5.02%	4.58%

Significant Accounting Policies - Investments in Commercial Real Estate Properties (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Investment in Commercial Real Estate Properties
Depreciable real estate reserves	$ 0	$ (56,272,000)
Rental revenue from amortization of acquired leases	2,400,000	4,800,000
Reduction in interest expense from amortization of above-market rate mortgages	0	$ 700,000
Identified intangible assets (included in other assets):
Gross amount	282,288,000		$ 325,880,000
Accumulated amortization	(241,043,000)		(277,038,000)
Net	41,245,000		48,842,000
Identified intangible liabilities (included in deferred revenue):
Gross amount	359,469,000		540,283,000
Accumulated amortization	(256,685,000)		(402,583,000)
Net	102,784,000		137,700,000
Net intangible assets reclassed to assets held for sale	100,000		13,900,000
Net intangible liabilities reclassed to liabilities relates to assets held for sale	$ 100,000		$ 4,100,000.0
Minimum \| Above-market leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	1 year
Minimum \| Below-market leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	1 year
Minimum \| In-place leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	1 year
Maximum \| Above-market leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	14 years
Maximum \| Below-market leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	14 years
Maximum \| In-place leases
Investment in Commercial Real Estate Properties
Estimated useful life of other intangible assets (in years)	14 years
Building \| Minimum
Investment in Commercial Real Estate Properties
Estimated useful life (in years)	3 years
Building \| Maximum
Investment in Commercial Real Estate Properties
Estimated useful life (in years)	40 years

Significant Accounting Policies - Investment in Marketable Securities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Investment in Marketable Securities
Marketable securities		$ 28,252,000	$ 28,579,000
Proceeds from sale of marketable securities	$ 54,400,000
Marketable Securities, Realized Gain (Loss)	$ 3,300,000
Fair Value
Investment in Marketable Securities
Marketable securities		28,252,000	28,579,000
Equity marketable securities
Investment in Marketable Securities
Cost basis		0	0
Commercial mortgage-backed securities
Investment in Marketable Securities
Marketable securities		28,252,000	28,579,000
Cost basis		$ 27,500,000	$ 27,500,000

Significant Accounting Policies - Reserve for Credit Losses (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accounting Policies [Abstract]
Loan reserves	$ 0	$ 0

Significant Accounting Policies - Revenue Recognition/Income Taxes (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Income taxes
Federal, state and local tax provision	$ 0.5

Significant Accounting Policies - Concentrations of Credit Risk/Accounting Standards Updates (Details) $ in Billions	3 Months Ended
	Mar. 31, 2018 USD ($) Tenant
Annualized rent \| Customer concentration
Concentration of Credit Risk
Number of tenants (tenants) \| Tenant	1
Maximum percentage of annualized rent for any one tenant not individually disclosed (percent) (more than)	5.00%
Annualized rent \| 1515 Broadway \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	5.80%
Annualized rent \| 11 Madison Avenue \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	7.30%
Annualized rent \| 1185 Avenue of the Americas \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	7.30%
Annualized rent \| 420 Lexington Avenue \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	6.30%
Annualized rent \| 1 Madison Ave \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	5.70%
Tenant 1 \| Annualized rent \| Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)	8.20%
1515 Broadway \| Accounting Standards Update 2017-05
Concentration of Credit Risk
Gain on disposal \| $	$ 0.6

Properties Held for Sale and Property Dispositions (Details) $ in Millions		1 Months Ended
	May 09, 2018 USD ($)	Jan. 31, 2018 USD ($) ft²	Mar. 31, 2018 USD ($) ft²
Properties Sold [Abstract]
Approximate Square Feet \| ft²			32,449,593
International Drive 1-6
Properties Sold [Abstract]
Sales Price			$ 55.0
115-117 Stevens Avenue
Properties Sold [Abstract]
Sales Price			$ 12.0
600 Lexington Ave
Properties Sold [Abstract]
Approximate Square Feet \| ft²		303,515
Sales Price		$ 305.0
Gain on Sale (Loss)		$ 23.8
Subsequent Event \| 635 Madison Avenue
Properties Sold [Abstract]
Sales Price	$ 151.0
Charge expected to be recorded	$ 14.0

Debt and Preferred Equity Investments - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2014
Mortgage Loans on Real Estate [Line Items]
Aggregate weighted average current yield (as a percent)	9.19%
Debt Investments Held [Abstract]
Carrying Value	$ 2,085,871,000	$ 2,114,041,000
Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017
Debt Investments Held [Abstract]
Carrying Value	250,500,000	0	$ 0
Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Amount participated out	1,300,000
Mezzanine Loan, with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000,000
Mezzanine Loan with an Initial Maturity Date of December 2018
Debt Investments Held [Abstract]
Amount participated out	14,600,000
Mezzanine Loan with an Initial Maturity Date of December 2018, 2
Debt Investments Held [Abstract]
Amount participated out	14,100,000
Mezzanine Loan with an Initial Maturity of March 2019
Debt Investments Held [Abstract]
Amount participated out	5,100,000
Debt Investments in Mortgage Loans
Debt Investments Held [Abstract]
Future Funding Obligations	199,445,000
Senior Financing	7,120,078,000
Carrying Value	1,941,045,000	1,969,618,000
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	3,896,080,000
Carrying Value	672,652,000	669,968,000
Total fixed rate \| Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	250,464,000	250,464,000
Interest Receivable	7,700,000
Total fixed rate \| Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	26,380,000	26,366,000
Loan acquired				$ 26,400,000
Discount amount				200,000
Total fixed rate \| Mortgage Loan, August 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	201,000	239,000
Total fixed rate \| Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,160,000,000
Carrying Value	206,230,000	204,005,000
Total fixed rate \| Mezzanine Loan, September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000,000
Carrying Value	3,500,000	3,500,000
Total fixed rate \| Mezzanine Loan with an Initial Maturity Date of April 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	147,000,000
Carrying Value	24,918,000	24,913,000
Total fixed rate \| Mezzanine Loan, November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	86,580,000
Carrying Value	12,701,000	12,699,000
Total fixed rate \| Mezzanine Loan, with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	115,000,000
Carrying Value	12,934,000	12,932,000
Total fixed rate \| Mezzanine Loan, January 2025
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	95,000,000
Carrying Value	30,000,000	30,000,000
Total fixed rate \| Mezzanine Loan with an Initial Maturity Date of November 2026
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	340,000,000
Carrying Value	15,000,000	15,000,000
Total fixed rate \| Mezzanine Loan with an Initial Maturity Date of June 2027
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,657,500,000
Carrying Value	55,250,000	55,250,000
Total fixed rate \| Junior Mortgage Participation, Related To Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Loan acquired				5,700,000
Discount amount				$ 5,700,000
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	199,445,000
Senior Financing	3,223,998,000
Carrying Value	1,268,393,000	1,299,650,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	5,993,000
Senior Financing	294,036,000
Carrying Value	48,490,000	0
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of December 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	75,014,000
Carrying Value	23,346,000	34,947,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of April 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	40,000,000
Carrying Value	19,999,000	19,982,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of August 2018
Debt Investments Held [Abstract]
Future Funding Obligations	523,000
Senior Financing	20,523,000
Carrying Value	10,952,000	10,934,000
Total floating rate \| Mortgage/Mezzanine Loan, with an Initial Maturity Date of August 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	19,965,000	19,940,000
Total floating rate \| Mezzanine Loan With An Initial Maturity Date of August 2018, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	65,000,000
Carrying Value	14,973,000	14,955,000
Total floating rate \| Mortgage/Mezzanine Loan, September 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	16,980,000	16,969,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of September 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	37,500,000
Carrying Value	14,908,000	14,855,000
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity Date of October 2016 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	391,000
Senior Financing	0
Carrying Value	23,609,000	23,609,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of October 2018
Debt Investments Held [Abstract]
Future Funding Obligations	2,325,000
Senior Financing	45,025,000
Carrying Value	34,975,000	34,879,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of December 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	85,000,000
Carrying Value	15,327,000	15,381,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of December 2018, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	65,000,000
Carrying Value	14,816,000	14,869,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of December 2018, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	33,000,000
Carrying Value	26,947,000	26,927,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of December 2018, 4
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	175,000,000
Carrying Value	59,797,000	59,723,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of January 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	45,000,000
Carrying Value	12,192,000	12,174,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of January 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations	4,493,000
Senior Financing	27,852,000
Carrying Value	9,457,000	8,550,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of March 2019
Debt Investments Held [Abstract]
Future Funding Obligations	795,000
Senior Financing	0
Carrying Value	15,150,000	15,148,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of March 2019, 2 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	38,000,000
Carrying Value	21,951,000	21,939,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of April 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	175,000,000
Carrying Value	37,307,000	37,250,000
Total floating rate \| Mezzanine Loan with an Initial Maturity Date of April 2019, 2 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	265,000,000
Carrying Value	24,862,000	24,830,000
Total floating rate \| Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations	24,587,000
Senior Financing	208,094,000
Carrying Value	74,944,000	71,832,000
Total floating rate \| Mezzanine Loan, Maturity of September 2019
Debt Investments Held [Abstract]
Future Funding Obligations	2,034,000
Senior Financing	189,829,000
Carrying Value	37,867,000	37,851,000
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity of September 2019
Debt Investments Held [Abstract]
Future Funding Obligations	22,570,000
Senior Financing	0
Carrying Value	146,517,000	143,919,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of October 2019 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	350,000,000
Carrying Value	34,773,000	34,737,000
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity Date of December 2019 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	1,792,000
Senior Financing	0
Carrying Value	66,026,000	0
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations	21,303,000
Senior Financing	0
Carrying Value	48,245,000	43,845,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations	1,592,000
Senior Financing	568,461,000
Carrying Value	77,927,000	75,834,000
Total floating rate \| Mortgage Loan with an Initial Maturity of February 2020 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	16,038,000
Senior Financing	0
Carrying Value	83,465,000	0
Total floating rate \| Mezzanine Loan with an Initial Maturity of July 2020 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	6,654,000
Senior Financing	35,112,000
Carrying Value	11,539,000	11,259,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of July 2020 [Domain]
Debt Investments Held [Abstract]
Future Funding Obligations	47,557,000
Senior Financing	326,552,000
Carrying Value	79,477,000	75,428,000
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity of December 2020 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	40,798,000
Senior Financing	0
Carrying Value	90,789,000	88,989,000
Total floating rate \| Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	35,179,000	35,152,000
Total floating rate \| Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	60,000,000
Carrying Value	15,642,000	15,635,000
Total floating rate \| Mezzanine Loan with an Initial Maturity of August 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	280,000,000
Carrying Value	35,074,000	34,600,000
Total floating rate \| Mortgage/Mezzanine Loan repaid in June 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	162,553,000
Total floating rate \| Mezzanine Loan Contributed for a Joint Venture Interest
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	$ 0	$ 74,755,000

Debt and Preferred Equity Investments - Rollforward of Net Book Balance (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of period	$ 2,114,041	$ 1,640,412
Redemptions/Sales/Syndications/Amortization	(263,614)	(813,418)
Balance at end of period	2,085,871	2,114,041
Debt Investments in Mortgage Loans
Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	233,370	1,142,591
Preferred equity investments
Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	$ 2,074	$ 144,456

Debt and Preferred Equity Investments - Preferred Equity Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Preferred equity investment
Aggregate weighted average current yield (as a percent)	9.19%
Carrying Value	$ 2,085,871	$ 2,114,041
Preferred Equity, April 2021
Preferred equity investment
Future Funding Obligations	0
Senior Financing	272,000
Carrying Value	$ 144,826	144,423
Preferred equity investments
Preferred equity investment
Aggregate weighted average current yield (as a percent)	6.97%
Future Funding Obligations	$ 0
Senior Financing	272,000
Carrying Value	$ 144,826	$ 144,423

Debt and Preferred Equity Investments - Narrative (Details)	3 Months Ended		37 Months Ended
	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Preferred equity investment
Carrying Value	$ 2,085,871,000			$ 2,114,041,000
Number of portfolio segments of financial receivables (segment) \| segment	1	1
Additional amount of financing receivables included in other assets	$ 88,000,000			65,500,000
Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017
Preferred equity investment
Carrying Value	250,500,000			0	$ 0
Junior Mortgage Participation Acquired in September 2014
Preferred equity investment
Payments to acquire loans			$ 0
Carrying Value	$ 0			$ 0	$ 0

Investments in Unconsolidated Joint Ventures - Additional Information (Details) $ in Thousands		1 Months Ended				3 Months Ended
	Jan. 01, 2018 USD ($)	Feb. 28, 2018	Nov. 30, 2017	May 31, 2017 USD ($)	Oct. 31, 2016	Mar. 31, 2018 USD ($) ft² unit	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
General information on each joint venture
Net equity investment in VIEs in which the entity is not primary beneficiary						$ 631,400		$ 606,200
Unaudited Approximate Square Feet (sqft) \| ft²						32,449,593
Purchase price and other fair value adjustments						$ 49,293	$ 0
100 Park Avenue
General information on each joint venture
Ownership Interest						49.90%
Unaudited Approximate Square Feet (sqft) \| ft²						834,000
Acquisition Price						$ 95,800
717 Fifth Avenue
General information on each joint venture
Ownership Interest						10.92%
Unaudited Approximate Square Feet (sqft) \| ft²						119,500
Acquisition Price						$ 251,900
800 Third Avenue
General information on each joint venture
Ownership Interest						60.52%
Unaudited Approximate Square Feet (sqft) \| ft²						526,000
Acquisition Price						$ 285,000
1745 Broadway
General information on each joint venture
Ownership Interest						56.87%
Unaudited Approximate Square Feet (sqft) \| ft²						674,000
Acquisition Price						$ 520,000
Jericho Plaza
General information on each joint venture
Ownership Interest						11.67%
Unaudited Approximate Square Feet (sqft) \| ft²						640,000
Acquisition Price						$ 210,000
11 West 34th Street
General information on each joint venture
Ownership Interest						30.00%
Unaudited Approximate Square Feet (sqft) \| ft²						17,150
Acquisition Price						$ 10,800
3 Columbus Circle
General information on each joint venture
Ownership Interest						48.90%
Unaudited Approximate Square Feet (sqft) \| ft²						741,500
Acquisition Price						$ 500,000
280 Park Avenue
General information on each joint venture
Ownership Interest						50.00%
Unaudited Approximate Square Feet (sqft) \| ft²						1,219,158
Acquisition Price						$ 400,000
1552-1560 Broadway
General information on each joint venture
Ownership Interest						50.00%
Unaudited Approximate Square Feet (sqft) \| ft²						57,718
Acquisition Price						$ 136,550
724 Fifth Avenue
General information on each joint venture
Ownership Interest						50.00%
Unaudited Approximate Square Feet (sqft) \| ft²						65,010
Acquisition Price						$ 223,000
10 East 53rd Street
General information on each joint venture
Ownership Interest						55.00%
Unaudited Approximate Square Feet (sqft) \| ft²						354,300
Acquisition Price						$ 252,500
521 Fifth Avenue
General information on each joint venture
Ownership Interest						50.50%
Unaudited Approximate Square Feet (sqft) \| ft²						460,000
Acquisition Price						$ 315,000
21 East 66th Street
General information on each joint venture
Ownership Interest						32.28%
Unaudited Approximate Square Feet (sqft) \| ft²						13,069
Acquisition Price						$ 75,000
650 Fifth Avenue
General information on each joint venture
Ownership Interest						50.00%
Unaudited Approximate Square Feet (sqft) \| ft²						69,214
Acquisition Price						$ 0
121 Greene Street
General information on each joint venture
Ownership Interest						50.00%
Unaudited Approximate Square Feet (sqft) \| ft²						7,131
Acquisition Price						$ 27,400
175-225 Third Street Brooklyn, New York
General information on each joint venture
Ownership Interest						95.00%
Unaudited Approximate Square Feet (sqft) \| ft²						0
Acquisition Price						$ 74,600
55 West 46th Street
General information on each joint venture
Ownership Interest						25.00%
Unaudited Approximate Square Feet (sqft) \| ft²						347,000
Acquisition Price						$ 295,000
Stonehenge Portfolio
General information on each joint venture
Ownership Interest					90.00%
Unaudited Approximate Square Feet (sqft) \| ft²						1,439,016
Acquisition Price						$ 36,668
131-137 Spring Street
General information on each joint venture
Ownership Interest						20.00%
Unaudited Approximate Square Feet (sqft) \| ft²						68,342
Acquisition Price						$ 277,750
605 West 42nd Street
General information on each joint venture
Ownership Interest						20.00%
Unaudited Approximate Square Feet (sqft) \| ft²						927,358
Acquisition Price						$ 759,000
11 Madison Avenue
General information on each joint venture
Ownership Interest						60.00%
Unaudited Approximate Square Feet (sqft) \| ft²						2,314,000
Acquisition Price						$ 2,605,000
333 East 22nd St
General information on each joint venture
Ownership Interest						33.33%
Economic Interest (as a percent)						33.33%
Unaudited Approximate Square Feet (sqft) \| ft²						26,926
Acquisition Price						$ 0
East 400 Street 57
General information on each joint venture
Ownership Interest					51.00%	51.00%
Unaudited Approximate Square Feet (sqft) \| ft²						290,482
Acquisition Price						$ 170,000
1552 Broadway
General information on each joint venture
Unaudited Approximate Square Feet (sqft) \| ft²						13,045
One Vanderbilt
General information on each joint venture
Ownership Interest						71.01%
Unaudited Approximate Square Feet (sqft) \| ft²						0
Acquisition Price						$ 3,310,000
Aggregate equity committed by partners						$ 525,000
Maximum ownership percentage of partners						29.00%
Partners' ownership percentage						6.84%
Equity method investment, amount sold				$ 10,000
Worldwide Plaza
General information on each joint venture
Ownership Interest						24.35%
Economic Interest (as a percent)						24.35%
Unaudited Approximate Square Feet (sqft) \| ft²						2,048,725
Acquisition Price						$ 1,725,000
1515 Broadway
General information on each joint venture
Ownership Interest						56.87%
Economic Interest (as a percent)						56.87%
Unaudited Approximate Square Feet (sqft) \| ft²						1,750,000
Acquisition Price						$ 1,950,000
Cumulative effect on retained earnings	$ 600,000
East 400 Street 57
General information on each joint venture
Ownership percentage in disposed asset					49.00%
21 East 66th Street \| Three Retail and Two Residential Units
General information on each joint venture
Ownership Interest						3228.00%
Number of stores \| unit						3
Number of residential units \| unit						2
21 East 66th Street \| Three Residential Units
General information on each joint venture
Ownership Interest						1614.00%
Number of residential units \| unit						3
Mezzanine Loan
General information on each joint venture
Ownership Interest				33.33%		33.33%
Economic Interest (as a percent)						33.33%
Unaudited Approximate Square Feet (sqft) \| ft²						0
Acquisition Price						$ 15,000
Allianz Real Estate \| 1515 Broadway
General information on each joint venture
Ownership percentage in disposed asset		13.00%	30.00%
Joint venture \| 100 Park Avenue
General information on each joint venture
Economic Interest (as a percent)						49.90%
Joint venture \| 717 Fifth Avenue
General information on each joint venture
Economic Interest (as a percent)						10.92%
Joint venture \| 800 Third Avenue
General information on each joint venture
Economic Interest (as a percent)						60.52%
Joint venture \| 1745 Broadway
General information on each joint venture
Economic Interest (as a percent)						56.87%
Joint venture \| Jericho Plaza
General information on each joint venture
Economic Interest (as a percent)						11.67%
Joint venture \| 11 West 34th Street
General information on each joint venture
Economic Interest (as a percent)						30.00%
Joint venture \| 3 Columbus Circle
General information on each joint venture
Economic Interest (as a percent)						48.90%
Joint venture \| 280 Park Avenue
General information on each joint venture
Economic Interest (as a percent)						50.00%
Joint venture \| 1552-1560 Broadway
General information on each joint venture
Economic Interest (as a percent)						50.00%
Joint venture \| 724 Fifth Avenue
General information on each joint venture
Economic Interest (as a percent)						50.00%
Joint venture \| 10 East 53rd Street
General information on each joint venture
Economic Interest (as a percent)						55.00%
Joint venture \| 521 Fifth Avenue
General information on each joint venture
Economic Interest (as a percent)						50.50%
Joint venture \| 21 East 66th Street
General information on each joint venture
Economic Interest (as a percent)						32.28%
Joint venture \| 650 Fifth Avenue
General information on each joint venture
Economic Interest (as a percent)						50.00%
Joint venture \| 121 Greene Street
General information on each joint venture
Economic Interest (as a percent)						50.00%
Joint venture \| 175-225 Third Street Brooklyn, New York
General information on each joint venture
Economic Interest (as a percent)						95.00%
Joint venture \| 55 West 46th Street
General information on each joint venture
Economic Interest (as a percent)						25.00%
Joint venture \| Stonehenge Portfolio
General information on each joint venture
Ownership Interest					10.00%
Joint venture \| 131-137 Spring Street
General information on each joint venture
Economic Interest (as a percent)						20.00%
Joint venture \| 605 West 42nd Street
General information on each joint venture
Economic Interest (as a percent)						20.00%
Joint venture \| 11 Madison Avenue
General information on each joint venture
Economic Interest (as a percent)						60.00%
Joint venture \| East 400 Street 57
General information on each joint venture
Economic Interest (as a percent)						41.00%
Joint venture \| One Vanderbilt
General information on each joint venture
Economic Interest (as a percent)						71.01%
Joint venture \| 919 Third Avenue
General information on each joint venture
Ownership Interest						51.00%
Economic Interest (as a percent)						51.00%
Unaudited Approximate Square Feet (sqft) \| ft²						1,454,000
Acquisition Price						$ 1,256,727

Investments in Unconsolidated Joint Ventures - Acquisition, Development and Construction Arrangements/Sale of Joint Venture Interest or Property (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	Mar. 31, 2018	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Oct. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 3,034,596		$ 3,034,596		$ 2,362,989
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate			(6,440)	$ 2,047
Stonehenge Portfolio
Schedule of Equity Method Investments [Line Items]
Ownership Interest						90.00%
Mezzanine loan due July 2036
Schedule of Equity Method Investments [Line Items]
Equity method investments	27,628		27,628		26,716
Mezzanine loan due February 2022
Schedule of Equity Method Investments [Line Items]
Equity method investments	44,751		44,751		44,823
Mezzanine Loan and Preferred Equity, Due March 2018
Schedule of Equity Method Investments [Line Items]
Equity method investments	0		0		100,000
Mezzanine Loans And Preferred Equity [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 72,379		$ 72,379		$ 171,539
Stonehenge Portfolio
Schedule of Equity Method Investments [Line Items]
Ownership Interest	5.00%	9.83%	5.00%
Gross Asset Valuation	$ 287,000	$ 44,100	$ 287,000
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	$ (5,701)	$ (362)
1515 Broadway
Schedule of Equity Method Investments [Line Items]
Ownership Interest		13.00%
Gross Asset Valuation		$ 1,950,000
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate		$ 0

Investments in Unconsolidated Joint Ventures - Mortgages and Other Loans Payable (Details)	1 Months Ended		3 Months Ended
	Apr. 30, 2018	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($) extension	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Total fixed rate debt		$ 1,891,154,000	$ 1,891,154,000	$ 2,400,560,000
Total floating rate debt		565,026,000	565,026,000	465,431,000
Total fixed rate and floating rate debt		2,456,180,000	2,456,180,000	2,865,991,000
919 Third Avenue
Debt Instrument [Line Items]
Total fixed rate debt		$ 0	$ 0	500,000,000
1515 Broadway
Debt Instrument [Line Items]
Economic Interest (as a percent)		56.87%	56.87%
Worldwide Plaza
Debt Instrument [Line Items]
Economic Interest (as a percent)		24.35%	24.35%
Joint venture
Debt Instrument [Line Items]
Total fixed rate debt		$ 6,014,627,000	$ 6,014,627,000	5,569,138,000
Total floating rate debt		3,983,061,000	3,983,061,000	3,979,066,000
Total fixed rate and floating rate debt		9,997,688,000	9,997,688,000	9,548,204,000
Deferred financing costs, net		(120,809,000)	(120,809,000)	(136,103,000)
Total joint venture mortgages and other loans payable, net		$ 9,876,879,000	$ 9,876,879,000	9,412,101,000
Joint venture \| 521 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.50%	50.50%
Interest rate, fixed rate debt (as a percent)		3.73%	3.73%
Total fixed rate debt		$ 170,000,000	$ 170,000,000	170,000,000
Joint venture \| 717 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		10.92%	10.92%
Joint venture \| 717 Fifth Avenue \| Mortgage loan
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		4.45%	4.45%
Total fixed rate debt		$ 300,000,000	$ 300,000,000	300,000,000
Committed amount		$ 300,000,000	$ 300,000,000
Joint venture \| 717 Fifth Avenue \| Mezzanine loans
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		5.50%	5.50%
Total fixed rate debt		$ 355,328,000	$ 355,328,000	355,328,000
Committed amount		$ 355,300,000	$ 355,300,000
Joint venture \| 650 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.00%	50.00%
Joint venture \| 650 Fifth Avenue \| Mortgage loan
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		4.46%	4.46%
Total fixed rate debt		$ 210,000,000	$ 210,000,000	210,000,000
Long-term debt, carrying value		$ 210,000,000	$ 210,000,000
Joint venture \| 650 Fifth Avenue \| Mezzanine loans
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		5.45%	5.45%
Total fixed rate debt		$ 65,000,000	$ 65,000,000	65,000,000
Joint venture \| 21 East 66th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		32.28%	32.28%
Interest rate, fixed rate debt (as a percent)		3.60%	3.60%
Interest rate, floating rate debt (as a percent)		2.75%	2.75%
Total fixed rate debt		$ 12,000,000	$ 12,000,000	12,000,000
Total floating rate debt		$ 1,628,000	$ 1,628,000	1,648,000
Joint venture \| 919 Third Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		51.00%	51.00%
Interest rate, fixed rate debt (as a percent)		5.12%	5.12%
Total fixed rate debt		$ 500,000,000	$ 500,000,000	0
Joint venture \| 3 Columbus Circle
Debt Instrument [Line Items]
Economic Interest (as a percent)		48.90%	48.90%
Interest rate, fixed rate debt (as a percent)		3.61%	3.61%
Total fixed rate debt		$ 350,000,000	$ 350,000,000	350,000,000
Joint venture \| 1515 Broadway
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		3.93%	3.93%
Total fixed rate debt		$ 868,309,000	$ 868,309,000	872,528,000
Joint venture \| 11 Madison Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		60.00%	60.00%
Interest rate, fixed rate debt (as a percent)		3.84%	3.84%
Total fixed rate debt		$ 1,400,000,000	$ 1,400,000,000	1,400,000,000
Joint venture \| 800 Third Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		60.52%	60.52%
Interest rate, fixed rate debt (as a percent)		3.37%	3.37%
Total fixed rate debt		$ 177,000,000	$ 177,000,000	177,000,000
Joint venture \| East 400 Street 57
Debt Instrument [Line Items]
Economic Interest (as a percent)		41.00%	41.00%
Interest rate, fixed rate debt (as a percent)		3.00%	3.00%
Total fixed rate debt		$ 100,000,000	$ 100,000,000	100,000,000
Joint venture \| Worldwide Plaza
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		3.98%	3.98%
Total fixed rate debt		$ 1,200,000,000	$ 1,200,000,000	1,200,000,000
Joint venture \| Stonehenge Portfolio
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)		4.25%	4.25%
Interest rate, floating rate debt (as a percent)		1.40%	1.40%
Total fixed rate debt		$ 306,990,000	$ 306,990,000	357,282,000
Total floating rate debt		$ 38,000,000	$ 38,000,000	55,340,000
Joint venture \| 1745 Broadway
Debt Instrument [Line Items]
Economic Interest (as a percent)		56.87%	56.87%
Interest rate, floating rate debt (as a percent)		1.85%	1.85%
Total floating rate debt		$ 345,000,000	$ 345,000,000	345,000,000
Joint venture \| 1745 Broadway \| Mortgage loan
Debt Instrument [Line Items]
Committed amount		375,000,000	375,000,000
Unfunded amount		$ 30,000,000	$ 30,000,000
Joint venture \| 55 West 46th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		25.00%	25.00%
Interest rate, floating rate debt (as a percent)		2.13%	2.13%
Total floating rate debt		$ 172,511,000	$ 172,511,000	171,444,000
Committed amount		195,000,000	195,000,000
Unused borrowing capacity, amount		$ 22,500,000	$ 22,500,000
Joint venture \| 175-225 Third Street Brooklyn, New York
Debt Instrument [Line Items]
Economic Interest (as a percent)		95.00%	95.00%
Interest rate, floating rate debt (as a percent)		1.00%	1.00%
Total floating rate debt		$ 40,000,000	$ 40,000,000	40,000,000
Joint venture \| Jericho Plaza
Debt Instrument [Line Items]
Economic Interest (as a percent)		11.67%	11.67%
Interest rate, floating rate debt (as a percent)		4.15%	4.15%
Total floating rate debt		$ 81,922,000	$ 81,922,000	81,099,000
Extension option exercised,term		12 months
Term (in Years)			2 years
Face amount of loan		$ 100,000,000	$ 100,000,000
Joint venture \| 724 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.00%	50.00%
Interest rate, floating rate debt (as a percent)		2.42%	2.42%
Total floating rate debt		$ 275,000,000	$ 275,000,000	275,000,000
Joint venture \| 1552 Broadway
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.00%	50.00%
Interest rate, floating rate debt (as a percent)		2.65%	2.65%
Total floating rate debt		$ 195,000,000	$ 195,000,000	195,000,000
Joint venture \| 280 Park Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.00%	50.00%
Interest rate, floating rate debt (as a percent)		1.73%	1.73%
Total floating rate debt		$ 1,200,000,000	$ 1,200,000,000	1,200,000,000
Joint venture \| 121 Greene Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		50.00%	50.00%
Interest rate, floating rate debt (as a percent)		1.50%	1.50%
Total floating rate debt		$ 15,000,000	$ 15,000,000	15,000,000
Joint venture \| 10 East 53rd Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		55.00%	55.00%
Interest rate, floating rate debt (as a percent)		2.25%	2.25%
Total floating rate debt		$ 170,000,000	$ 170,000,000	170,000,000
Joint venture \| 131-137 Spring Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		20.00%	20.00%
Interest rate, floating rate debt (as a percent)		1.55%	1.55%
Total floating rate debt		$ 141,000,000	$ 141,000,000	141,000,000
Joint venture \| 11 West 34th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		30.00%	30.00%
Interest rate, floating rate debt (as a percent)		1.45%	1.45%
Total floating rate debt		$ 23,000,000	$ 23,000,000	23,000,000
Joint venture \| 100 Park Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)		49.90%	49.90%
Interest rate, floating rate debt (as a percent)		1.75%	1.75%
Total floating rate debt		$ 360,000,000	$ 360,000,000	360,000,000
Joint venture \| One Vanderbilt
Debt Instrument [Line Items]
Economic Interest (as a percent)		71.01%	71.01%
Interest rate, floating rate debt (as a percent)		3.50%	3.50%
Total floating rate debt		$ 375,000,000	$ 375,000,000	355,535,000
Joint venture \| One Vanderbilt \| Construction Loans
Debt Instrument [Line Items]
Term (in Years)			5 years
Maximum facility capacity		$ 1,500,000,000.0	$ 1,500,000,000.0
Credit facility, interest rate (as a percent)			3.50%
Number of extension options \| extension			2
Period of extension options			1 year
Joint venture \| 605 West 42nd Street
Debt Instrument [Line Items]
Economic Interest (as a percent)		20.00%	20.00%
Interest rate, floating rate debt (as a percent)		1.44%	1.44%
Total floating rate debt		$ 550,000,000	$ 550,000,000	$ 550,000,000
Joint venture \| Subsequent Event \| 724 Fifth Avenue
Debt Instrument [Line Items]
Extension option exercised,term	12 months
Mezzanine Loan, Initial Maturity October 2022 [Member] \| Joint venture \| 650 Fifth Avenue \| Mezzanine loans
Debt Instrument [Line Items]
Long-term debt, carrying value		65,000,000	65,000,000
Secured Debt, Initial Maturity November 2017 [Member] \| Joint venture \| Stonehenge Portfolio
Debt Instrument [Line Items]
Total fixed rate debt		136,400,000	136,400,000
Secured Debt, Initial Maturity February 2027 [Member] \| Joint venture \| Stonehenge Portfolio
Debt Instrument [Line Items]
Total fixed rate debt		$ 170,600,000	$ 170,600,000

Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Assets (1)
Commercial real estate property, net	$ 6,828,550		$ 7,906,006
Cash and cash equivalents	288,808	$ 468,035	127,888
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	49,552		57,644
Other assets	360,556		310,688
Liabilities and equity (1)
Mortgages and other loans payable, net	2,433,994		2,837,282
Deferred revenue/gain	177,896		208,119
Other liabilities	103,654		188,005
Company's investments in unconsolidated joint ventures	3,034,596		2,362,989
Combined statements of income for the unconsolidated joint ventures
Operating expenses	59,782	74,506
Ground rent	8,308	8,308
Real estate taxes	45,661	61,068
Interest expense, net of interest income	47,916	65,622
Amortization of deferred financing costs	3,537	4,761
Transaction related costs	162	133
Depreciation and amortization	69,388	94,134
Total expenses	258,282	332,675
Company's equity in net income from unconsolidated joint ventures (1)	4,036	6,614
Joint venture
Investment in Unconsolidated Joint Ventures
Management fees, base revenue	3,800	5,400
Assets (1)
Commercial real estate property, net	14,652,483		12,822,133
Cash and cash equivalents	452,648		494,909
Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance	359,396		349,944
Debt and preferred equity investments, net	103,379		202,539
Other assets	2,361,367		1,407,806
Total assets	17,929,273		15,277,331
Liabilities and equity (1)
Mortgages and other loans payable, net	9,876,879		9,412,101
Deferred revenue/gain	1,911,564		985,648
Other liabilities	493,369		411,053
Members' equity	5,647,461		4,468,529
Total liabilities and members' equity	17,929,273		15,277,331
Company's investments in unconsolidated joint ventures	3,034,596		$ 2,362,989
Combined statements of income for the unconsolidated joint ventures
Total revenues	320,941	216,521
Operating expenses	59,773	38,794
Ground rent	4,393	4,251
Real estate taxes	57,027	34,939
Interest expense, net of interest income	89,741	55,328
Amortization of deferred financing costs	5,116	6,505
Transaction related costs	0	89
Depreciation and amortization	105,080	71,164
Total expenses	321,130	211,070
Net (loss) income before gain on sale (1)	(189)	5,451
Company's equity in net income from unconsolidated joint ventures (1)	$ 4,036	$ 6,614

Deferred Costs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred leasing costs	$ 415,824	$ 443,341
Less: accumulated amortization	(220,267)	(217,140)
Deferred costs, net	$ 195,557	$ 226,201

Mortgages and Other Loans Payable (Details)	3 Months Ended
Mortgages and Other Loans Payable (Details)	Mar. 31, 2018 USD ($) extension debt_instrument $ / shares	Apr. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 31, 2016 USD ($)
Debt Instrument [Line Items]
Total fixed rate debt	$ 1,891,154,000		$ 2,400,560,000
Total floating rate debt	565,026,000		465,431,000
Total fixed rate and floating rate debt	2,456,180,000		2,865,991,000
Mortgages reclassed to liabilities related to assets held for sale	0		0
Total mortgages and other loans payable	2,456,180,000		2,865,991,000
Deferred financing costs, net of amortization	(22,186,000)		(28,709,000)
Total mortgages and other loans payable, net	2,433,994,000		2,837,282,000
Book value of collateral	3,500,000,000		4,800,000,000
Outstanding under line of credit facility	0		30,336,000
Series J Preferred Units
Debt Instrument [Line Items]
Total fixed rate debt	4,000,000		4,000,000
Limited partnership interest	$ 4,000,000
Preferred units (as a percent)	3.75%
Preferred units, liquidation preference (in dollars per unit) \| $ / shares	$ 1,000.00
Series J Preferred Units \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.75%
Unsecured Loan
Debt Instrument [Line Items]
Total fixed rate debt	$ 16,000,000		16,000,000
Unsecured Loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.81%
Uncommitted Master Repurchase Agreements
Debt Instrument [Line Items]
Number of debt instruments \| debt_instrument	2
Uncommitted Master Repurchase Agreement 2017
Debt Instrument [Line Items]
Total floating rate debt	$ 189,883,000		90,809,000
Term (in Years)	1 year
Maximum facility capacity	$ 300,000,000.0
Number of extension options \| extension	2
Period of extension options	1 year
Outstanding under line of credit facility	$ 189,500,000
Uncommitted Master Repurchase Agreement 2017 \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.23%
Uncommitted Master Repurchase Agreement 2016
Debt Instrument [Line Items]
Term (in Years)	2 years
Maximum facility capacity				$ 300,000,000.0
Period of extension options	1 year
Basis point fee (as a percent)	0.25%
Outstanding under line of credit facility	$ (600,000)
Threshold amount for basis point fee to be applicable (less than)	$ 150,000,000.0
Uncommitted Master Repurchase Agreement 2016 \| Minimum \| LIBOR
Debt Instrument [Line Items]
Credit facility, interest rate (as a percent)	2.25%
Uncommitted Master Repurchase Agreement 2016 \| Maximum \| LIBOR
Debt Instrument [Line Items]
Credit facility, interest rate (as a percent)	4.00%
One Madison Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 477,843,000		486,153,000
One Madison Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.91%
762 Madison Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 771,000		771,000
762 Madison Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	5.00%
100 Church Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 216,240,000		217,273,000
100 Church Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.68%
420 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 300,000,000		300,000,000
420 Lexington Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.99%
400 East 58th Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 40,000,000		40,000,000
400 East 58th Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.00%
Term (in Years)	5 years
Landmark Square
Debt Instrument [Line Items]
Total fixed rate debt	$ 100,000,000		100,000,000
Landmark Square \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.90%
485 Lexington Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 450,000,000		450,000,000
485 Lexington Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.25%
1080 Amsterdam Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 36,300,000		36,363,000
Total fixed rate debt	35,500,000
Subordinate loan	$ 900,000
1080 Amsterdam Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.58%
Term (in Years)	5 years
1080 Amsterdam Avenue \| Mortgage loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	3.50%
1080 Amsterdam Avenue \| Subordinate loan \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	7.00%
315 West 33rd Street
Debt Instrument [Line Items]
Total fixed rate debt	$ 250,000,000		250,000,000
315 West 33rd Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)	4.17%
919 Third Avenue
Debt Instrument [Line Items]
Total fixed rate debt	$ 0		500,000,000
919 Third Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)
719 Seventh Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 42,143,000		41,622,000
719 Seventh Avenue \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	3.05%
183, 187 Broadway & 5-7 Dey Street
Debt Instrument [Line Items]
Total floating rate debt	$ 58,000,000		58,000,000
183, 187 Broadway & 5-7 Dey Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.70%
220 East 42nd Street
Debt Instrument [Line Items]
Total floating rate debt	$ 275,000,000		$ 275,000,000
220 East 42nd Street \| Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	1.60%
Subsequent Event \| Uncommitted Master Repurchase Agreement 2017
Debt Instrument [Line Items]
Maximum facility capacity		$ 400,000,000.0

Corporate Indebtedness - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) extension	Dec. 31, 2017 USD ($)
Corporate Indebtedness
Outstanding under line of credit facility	$ 0	$ 30,336,000
Term Loan B, Maturity November 21, 2024 \| Term loan
Corporate Indebtedness
Credit facility, maximum borrowing capacity	$ 200,000,000
Term Loan B, Maturity November 21, 2024 \| LIBOR \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.65%
Term Loan B, Maturity November 21, 2024 \| LIBOR \| Minimum \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.50%
Term Loan B, Maturity November 21, 2024 \| LIBOR \| Maximum \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	2.45%
Revolving credit facility
Corporate Indebtedness
Facility fee (as a percent)	0.20%
Outstanding under line of credit facility	$ 0
Revolving credit facility \| Minimum
Corporate Indebtedness
Facility fee (as a percent)	0.125%
Revolving credit facility \| Maximum
Corporate Indebtedness
Facility fee (as a percent)	0.30%
Term loan
Corporate Indebtedness
Credit facility, maximum borrowing capacity	$ 1,500,000,000
Term loan \| Line of Credit
Corporate Indebtedness
Long-term debt, carrying value	1,500,000,000	1,500,000,000
2012 Credit Facility
Corporate Indebtedness
Letters of credit	11,800,000
Ability to borrow under line of credit facility	1,500,000,000
2012 Credit Facility \| Line of Credit
Corporate Indebtedness
Long-term debt, carrying value	(9,200,000)	$ 30,300,000
Term Loan A, Maturity March 31, 2023 \| Term loan
Corporate Indebtedness
Credit facility, maximum borrowing capacity	$ 1,300,000,000.0
Term Loan A, Maturity March 31, 2023 \| LIBOR \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.10%
Term Loan A, Maturity March 31, 2023 \| LIBOR \| Minimum \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	0.90%
Term Loan A, Maturity March 31, 2023 \| LIBOR \| Maximum \| Term loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.75%
Revolving credit facility \| Revolving Credit Facility, Maturity March 31, 2022 \| Line of Credit
Corporate Indebtedness
Credit facility, maximum borrowing capacity	$ 1,500,000,000.0
Number of extensions \| extension	2
Term of extension	6 months
Maximum borrowing capacity, optional expansion	$ 4,500,000,000.0
Revolving credit facility \| Revolving Credit Facility, Maturity March 31, 2022 \| LIBOR \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.00%
Revolving credit facility \| Revolving Credit Facility, Maturity March 31, 2022 \| LIBOR \| Minimum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)	0.825%
Revolving credit facility \| Revolving Credit Facility, Maturity March 31, 2022 \| LIBOR \| Maximum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)	1.55%

Corporate Indebtedness - Senior Unsecured Notes (Details) - USD ($)	1 Months Ended	3 Months Ended
	Oct. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Debt disclosures by scheduled maturity date
Accreted Balance		$ 1,491,922,000	$ 1,491,575,000
Senior unsecured notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		1,400,000,000
Accreted Balance		1,404,406,000	1,404,605,000
Deferred financing costs, net		(8,086,000)	(8,666,000)
Accreted Balance, net of deferred financing costs		1,396,320,000	1,395,939,000
Senior unsecured notes \| 5.00% Senior unsecured notes maturing on August 15, 2018
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		250,000,000
Accreted Balance		$ 249,972,000	249,953,000
Coupon Rate (as a percent)		5.00%
Initial Term (in Years)		7 years
Senior unsecured notes \| 7.75% Senior unsecured notes maturing on March 15, 2020
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		$ 250,000,000
Accreted Balance		$ 250,000,000	250,000,000
Coupon Rate (as a percent)		7.75%
Initial Term (in Years)		10 years
Senior unsecured notes \| 4.50% Senior unsecured notes maturing on December 1, 2022
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		$ 300,000,000
Accreted Balance		$ 304,920,000	305,163,000
Coupon Rate (as a percent)		4.50%
Initial Term (in Years)		10 years
Senior unsecured notes \| 4.27% Senior unsecured notes maturing on December 17, 2025
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		$ 100,000,000
Accreted Balance		$ 100,000,000	100,000,000
Coupon Rate (as a percent)		4.27%
Initial Term (in Years)		10 years
Senior unsecured notes \| 3.25 Percent Senior Unsecured Notes Due October 2022
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		$ 500,000,000
Accreted Balance		$ 499,514,000	$ 499,489,000
Coupon Rate (as a percent)		3.25%
Initial Term (in Years)		5 years
Senior Unsecured Bonds \| 4.50% Senior Unsecured Bonds Due December 2022
Debt disclosures by scheduled maturity date
Coupon Rate (as a percent)	4.50%
Face amount of loan	$ 100,000,000.0
Redemption price, percentage	105.334%

Corporate Indebtedness - Junior Subordinated Deferrable Interest Debentures and Principal Maturities (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2005	Mar. 31, 2018
Principal Repayments and Joint Venture Debt
Remaining 2018		$ 352,555,000
2019		84,414,000
2020		1,142,880,000
2021		11,638,000
2022		1,007,985,000
Thereafter		2,856,708,000
Total principal repayments		$ 5,456,180,000
Trust Preferred Securities
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 100,000,000.0
LIBOR \| Trust Preferred Securities
Debt Instrument [Line Items]
Interest rate added to base rate (as a percent)		1.25%
Joint venture
Principal Repayments and Joint Venture Debt
Remaining 2018		$ 45,477,000
2019		262,460,000
2020		471,714,000
2021		454,571,000
2022		220,759,000
Thereafter		2,878,381,000
Total principal repayments		4,333,362,000
Joint venture \| Trust Preferred Securities
Principal Repayments and Joint Venture Debt
Remaining 2018		0
2019		0
2020		0
2021		0
2022		0
Thereafter		100,000,000
Total principal repayments		100,000,000
Joint venture \| Mortgages and other loans payable
Scheduled Amortization
Remaining 2018		28,555,000
2019		42,271,000
2020		23,466,000
2021		11,638,000
2022		9,430,000
Thereafter		16,591,000
Total amortization of debt		131,951,000
Principal Repayments and Joint Venture Debt
Remaining 2018		74,000,000
2019		42,143,000
2020		869,414,000
2021		0
2022		198,555,000
Thereafter		1,140,117,000
Total principal repayments		2,324,229,000
Joint venture \| Revolving Credit Facility
Principal Repayments and Joint Venture Debt
Remaining 2018		0
2019		0
2020		0
2021		0
2022		0
Thereafter		0
Total principal repayments		0
Joint venture \| Unsecured Term Loans
Principal Repayments and Joint Venture Debt
Remaining 2018		0
2019		0
2020		0
2021		0
2022		0
Thereafter		1,500,000,000
Total principal repayments		1,500,000,000
Joint venture \| Senior Unsecured Notes
Principal Repayments and Joint Venture Debt
Remaining 2018		250,000,000
2019		0
2020		250,000,000
2021		0
2022		800,000,000
Thereafter		100,000,000
Total principal repayments		$ 1,400,000,000

Corporate Indebtedness - Schedule of Consolidated Interest Expense, Excluding Capitalized Interest (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest expense
Interest expense before capitalized interest	$ 54,918	$ 72,422
Interest capitalized	(6,686)	(6,279)
Interest income	(316)	(521)
Interest expense, net	$ 47,916	$ 65,622

Related Party Transactions (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Amounts due from/to related parties
Due from joint ventures		$ 21,972		$ 15,025
Other		9,333		8,014
Related party receivables		31,305		$ 23,039
Alliance Building Services
Related Party Transactions
Profit participation from related party		1,000	$ 800
Payments made for services		4,000	$ 4,500
Entity with Stephen L Green ownership interest
Related Party Transactions
Property management fees from related party		100
One Vanderbilt \| Marc Holliday
Related Party Transactions
Due from related party		1,400
One Vanderbilt \| Andrew Mathias
Related Party Transactions
Due from related party		$ 1,000
One Vanderbilt \| Minimum \| Marc Holliday
Related Party Transactions
Percentage of profits due to investors (as a percentage)	1.50%
One Vanderbilt \| Minimum \| Andrew Mathias
Related Party Transactions
Percentage of profits due to investors (as a percentage)	1.00%
One Vanderbilt \| Maximum \| Marc Holliday
Related Party Transactions
Percentage of profits due to investors (as a percentage)	1.80%
One Vanderbilt \| Maximum \| Andrew Mathias
Related Party Transactions
Percentage of profits due to investors (as a percentage)	1.20%

Noncontrolling Interests on the Company's Consolidated Financial Statements - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) shares $ / shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) shares	Mar. 31, 2016 shares	Aug. 31, 2015 shares	Jul. 31, 2015 shares	Jun. 30, 2015 shares	Feb. 28, 2015 shares	Aug. 31, 2014 shares
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period \| $	$ 461,954,000
Net income \| $	5,272,000	$ 476,000
Accumulated other comprehensive income allocation \| $	619,000	(199,000)
Balance at end of period \| $	$ 475,807,000		$ 461,954,000
Number of company common stock issued on conversion of Series B preferred units	6.71348
SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	5.02%		4.58%
Number of units of operating partnership owned by the noncontrolling interest unit holders (shares) \| shares	4,715,338		4,452,979
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	4,715,338.000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period \| $	$ 461,954,000	473,882,000	$ 473,882,000
Distributions \| $	(3,841,000)		(14,266,000)
Issuance of common units \| $	15,448,000		25,723,000
Redemption of common units \| $	0		(21,574,000)
Net income \| $	5,272,000		3,995,000
Accumulated other comprehensive income allocation \| $	619,000	$ (199,000)	(94,000)
Fair value adjustment \| $	(3,645,000)		(5,712,000)
Balance at end of period \| $	$ 475,807,000		$ 461,954,000
SL Green Operating Partnership \| Series G Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares	1,902,000
Dividend rate preferred units (as a percent)	4.50%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	1.125
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 88.50
Number of company common stock issue on redemption of operation partnership common units	1
SL Green Operating Partnership \| Series F Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares	60
Mandatory liquidation preference (in dollars per share) \| $	$ 1,000.00
SL Green Operating Partnership \| Series K Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares									563,954
Dividend rate preferred units (as a percent)	3.50%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	0.875
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 134.67
Preferred units, shares authorized (in shares) \| shares	700,000
SL Green Operating Partnership \| Series L Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares									378,634
Dividend rate preferred units (as a percent)	4.00%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	$ 1.00
Preferred units, shares authorized (in shares) \| shares	500,000
SL Green Operating Partnership \| Series M Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares								1,600,000
Dividend rate preferred units (as a percent)	3.75%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	$ 0.9375
Preferred units, shares authorized (in shares) \| shares	1,600,000
SL Green Operating Partnership \| Series N Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares							552,303
Dividend rate preferred units (as a percent)	3.00%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	$ 0.75
Preferred units, shares authorized (in shares) \| shares	552,303
SL Green Operating Partnership \| Series O Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	6.25%
Preferred units, shares authorized (in shares) \| shares	1
SL Green Operating Partnership \| Series P Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	200,000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares						200,000
Dividend rate preferred units (as a percent)	4.00%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	$ 1.00
SL Green Operating Partnership \| Series Q Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	268,000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares						268,000
Dividend rate preferred units (as a percent)	3.50%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	0.875
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 148.95
SL Green Operating Partnership \| Series R Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	400,000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares					400,000
Dividend rate preferred units (as a percent)	3.50%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	0.875
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 154.89
SL Green Operating Partnership \| Series S Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	1,077,280
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares					1,077,280
Dividend rate preferred units (as a percent)	4.00%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	$ 1.00
SL Green Operating Partnership \| Series T Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	230,000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares				230,000
Dividend rate preferred units (as a percent)	2.75%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	0.6875
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 119.02
SL Green Operating Partnership \| Series U Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	680,000
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares				680,000
Dividend rate preferred units (as a percent)	4.50%
Liquidation preference of preferred units (in dollars per share)	$ 25.00
Annual dividends on preferred units (in dollars per share)	1.125
SL Green Operating Partnership \| Series U Preferred Units \| Minimum
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Annual dividends on preferred units (in dollars per share)	$ 0.75
SL Green Operating Partnership \| Series A Preferred Units
Organization
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) \| shares	109,161
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares					109,161
Dividend rate preferred units (as a percent)	3.50%
Liquidation preference of preferred units (in dollars per share)	$ 1,000.00
Annual dividends on preferred units (in dollars per share)	$ 35.00
SL Green Operating Partnership \| Series B Preferred Units
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of preferred units issued (in shares) \| shares	0

Noncontrolling Interests on the Company's Consolidated Financial Statements - Common Unit Activity (Details) - SL Green Operating Partnership - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Rollforward Analysis of Preferred Unit Activity
Issuance of preferred units	$ 15,448	$ 25,723
Redemption of preferred units	0	(21,574)
Preferred Units
Rollforward Analysis of Preferred Unit Activity
Balance at beginning of period	301,735	302,010
Issuance of preferred units	0	0
Redemption of preferred units	(150)	(275)
Balance at end of period	$ 301,585	$ 301,735

Stockholders' Equity of the Company - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Aug. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Authorized capital stock (shares)	260,000,000	260,000,000
Authorized shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	160,000,000	160,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Excess stock, shares authorized (shares)	75,000,000	75,000,000
Excess stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	25,000,000	25,000,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Excess shares issued (shares)	0	0
Shares repurchased		3,653,928	8,342,411
Average price paid per share (in dollars per share)		$ 97.07	$ 101.64
2016 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 500,000,000	$ 1,000,000,000.0
Shares repurchased		11,996,339	8,342,411
Maximum approximate dollar value of shares that may yet be purchased under the plan	$ 297,200,000	$ 297,200,000	$ 652,000,000
Stock repurchase program, authorized amount	$ 1,500,000,000.0	$ 1,500,000,000.0
Repurchases of common stock (in shares)	142,004

Stockholders' Equity of the Company - Perpetual Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Aug. 31, 2012	Mar. 31, 2018	Dec. 31, 2017	Feb. 28, 2015
Stockholders' Equity
Common stock, shares authorized (in shares)		160,000,000	160,000,000
Series I Preferred Stock
Stockholders' Equity
Preferred stock, shares outstanding (in shares)		9,200,000	9,200,000
Dividend rate preferred units (as a percent)		6.50%
Perpetual preferred stock, liquidation preference (in dollars per share)		$ 25.00	$ 25.00
Perpetual preferred stock, annual dividends per share (in dollars per share)		$ 1.625
Contributions of net proceeds from sale of preferred stock	$ 221.9
Dividend Reinvestment and Stock Purchase Plan (DRIP)
Stockholders' Equity
Common stock, shares authorized (in shares)				3,500,000

Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic Earnings:
Income attributable to SL Green common stockholders	$ 101,766	$ 11,351
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 107,038	$ 11,827
Basic Shares:
Weighted average common shares outstanding (shares)	90,520,000	100,643,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	4,683,000	4,607,000
Stock-based compensation plans (shares)	53,000	304,000
Diluted weighted average common stock outstanding (shares)	95,256,000	105,554,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,210,802	1,025,419
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 5,272	$ 476

Partners' Capital of the Operating Partnership - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018 shares	Dec. 31, 2017 shares
Common Stock
Stockholders' Equity
Units outstanding (units)	89,135,000	92,803,000
SL Green Operating Partnership
Stockholders' Equity
Noncontrolling interest in the operating partnership (as a percent)	5.02%	4.58%
Number of units of operating partnership owned by the noncontrolling interest unit holders (units)	4,715,338	4,452,979
SL Green Operating Partnership \| Series I Preferred Units
Stockholders' Equity
Units outstanding (units)	9,200,000
Period of restriction to redeem OP Units	1 year
Conversion of stock, shares issued	1
SL Green Operating Partnership \| Common Stock
Stockholders' Equity
Units outstanding (units)	89,135,009

Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Denominator
Weighted average common shares outstanding (shares)	90,520,000	100,643,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,210,802	1,025,419
SL Green Operating Partnership
Numerator
Net income attributable to SLGOP common unitholders	$ 107,038	$ 11,827
Denominator
Weighted average common shares outstanding (shares)	95,203,000	105,250,000
Stock-based compensation plans (shares)	53,000	304,000
Diluted weighted average common units outstanding (shares)	95,256,000	105,554,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,210,802	1,025,419

Share-based Compensation - Additional Information (Details) $ / shares in Units, fungible_unit in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Aug. 31, 2014 shares	Mar. 31, 2018 USD ($) unit / shares unit fungible_unit $ / shares shares	Mar. 31, 2017 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares	Jan. 01, 2008 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options		$ 1,600,000	$ 1,600,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of commencement of option vesting, from date of grant (in years)		1 year
Exercise price of options granted, low end of the range (in dollars per share) \| $ / shares		$ 20.67
Exercise price of options granted, high end of the range (in dollars per share) \| $ / shares		$ 137.18
Remaining weighted average contractual life of the options outstanding (in years)		3 years 5 months
Remaining average contractual life of the options exercisable (in years)		2 years 10 months 15 days
Total unrecognized compensation cost related to unvested stock awards		$ 6,700,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)		1 year 2 months
Weighted average fair value of options granted during the period		$ 84,068		$ 3,816,652
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period (in years)		5 years
Options vesting period (in years)		1 year
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period (in years)		10 years
Options vesting period (in years)		5 years
Class O LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement by Share Based Payment Award, Preferred Unit Distributions as a Percentage of Common Unit Distributions		10.00%
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense		$ 3,134,975	9,809,749
Total unrecognized compensation cost related to unvested stock awards		$ 18,100,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)		2 years
Annual award vesting rate, low end of range (as a percent)		15.00%
Annual award vesting rate, high end of range (as a percent)		35.00%
Fair value of restricted stock vested during the period		$ 9,700,000		$ 9,400,000
Weighted average fair value of options granted during the period		$ 3,237,006	$ 9,905,986
Awards granted (in shares) \| shares		33,450	96,185
Awards outstanding (in shares) \| shares		3,327,116		3,298,216	3,202,031
LTIP units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of options granted during the period		$ 20,600,000		$ 20,500,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested stock awards		$ 9,700,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)		1 year 2 months
Share-based compensation		$ 6,900,000	$ 10,000,000
Third Amendment and Restated 2005 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum fungible units that may be granted (in shares) \| unit		27,030,000
Fungible units per share (in fungible units per share) \| unit / shares		3.74
Shares that may be issued if equal to fungible units (shares) (less than) \| shares		27,030,000
Fungible units \| fungible_unit		7.3
Third Amendment and Restated 2005 Stock Option and Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense		$ 1,600,000	2,000,000
Stock options, stock appreciation rights and other awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fungible units per share (in fungible units per share) \| unit / shares		0.73
Award expiration period (in years)		5 years
All other awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fungible units per share (in fungible units per share) \| unit / shares		1.0
Award expiration period (in years)		10 years
2014 Outperformance Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense			2,100,000
Capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options		$ 27,900,000
LTIP units earned (in shares) \| shares	610,000
Award period (in years)	3 years
Maximum award to be earned, if performance reaches maximum threshold, first performance period	0.333
Maximum award to be earned, if performance reaches maximum threshold, second performance period	0.667
2014 Outperformance Plan \| Vesting on August 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of units vested	50.00%
2014 Outperformance Plan \| Vesting on August 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of units vested	50.00%
Deferred Stock Compensation Plan for Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense		$ 2,200,000	$ 1,900,000
Maximum percentage of the annual retainer fee, chairman fees and meeting fees that may be deferred by non-employee directors (percent)		100.00%
Awards granted (in shares) \| shares		10,211
Shares issued (in shares) \| shares		9,266
Awards outstanding (in shares) \| shares		110,064
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (shares) \| shares						500,000
Duration of each offering period starting the first day of each calendar quarter (in months)		3 months
Discount from market price		85.00%
Shares of common stock issued (shares) \| shares		107,193

Share-based Compensation - Stock Options and Restricted Stock Activity (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Stock options
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Dividend yield (as a percent)	2.85%		2.51%
Expected life of option (in years)	3 years 6 months		4 years 4 months 24 days
Risk-free interest rate (as a percent)	2.48%		1.73%
Expected stock price volatility (as a percent)	22.00%		28.10%
Options Outstanding
Balance at beginning of period (in shares)	1,548,719	1,737,213	1,737,213
Granted (in shares)	6,000		174,000
Exercised (in shares)	(4,000)		(292,193)
Lapsed or cancelled (in shares)	(18,799)		(70,301)
Balance at end of period (in shares)	1,531,920		1,548,719
Options exercisable at end of period (in shares)	1,040,103		800,902
Total fair value of options granted during the period	$ 84,068		$ 3,816,652
Weighted Average Exercise Price
Balance at beginning of year (in dollars per share)	$ 101.48	$ 98.44	$ 98.44
Granted (in dollars per share)	97.91		105.66
Exercised (in dollars per share)	88.91		81.07
Lapsed or cancelled (in dollars per share)	111.39		121.68
Balance at end of period (in dollars per share)	101.37		101.48
Options exercisable at end of period (in dollars per share)	$ 98.25		$ 94.33
Restricted Stock Awards
Options Outstanding
Total fair value of options granted during the period	$ 3,237,006	$ 9,905,986
Summary of restricted stock
Balance at beginning of year (in shares)	3,298,216	3,202,031	3,202,031
Granted (in shares)	33,450	96,185
Cancelled (in shares)	(4,550)	0
Balance at end of period (in shares)	3,327,116		3,298,216
Vested during the period (in shares)	91,014	95,736

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	$ 6,589,454
Other comprehensive (loss) income before reclassifications	9,658
Amounts reclassified from accumulated other comprehensive income	311
Ending Balance	6,537,629
Deferred net losses from terminated hedges	2,700	$ 3,200
Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	12,542
Other comprehensive (loss) income before reclassifications	6,859
Amounts reclassified from accumulated other comprehensive income	310
Ending Balance	19,711
Net unrealized gain on marketable securities
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	1,042
Other comprehensive (loss) income before reclassifications	(315)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	727
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	18,604
Ending Balance	28,573
Joint venture \| Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	5,020
Other comprehensive (loss) income before reclassifications	3,114
Amounts reclassified from accumulated other comprehensive income	1
Ending Balance	$ 8,135

Fair Value Measurements (Details) - USD ($)	3 Months Ended
Fair Value Measurements (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Fair Value of Financial Instruments
Marketable securities	$ 28,252,000		$ 28,579,000
Interest rate cap and swap agreements (included in other assets)	23,629,000		16,692,000
Purchase price and other fair value adjustments	49,293,000	$ 0
Debt and preferred equity investments	2,085,871,000		2,114,041,000
Equity method investments	3,034,596,000		2,362,989,000
Additional amount of financing receivables included in other assets	88,000,000		65,500,000
Carrying Value
Fair Value of Financial Instruments
Debt and preferred equity investments	2,085,871,000		2,114,041,000
Fixed rate debt	3,795,560,000		4,305,165,000
Variable rate debt	1,665,026,000		1,605,431,000
Total	5,460,586,000		5,910,596,000
Fair Value
Fair Value of Financial Instruments
Marketable securities	28,252,000		28,579,000
Total	5,514,156,000		6,034,090,000
Estimated fair value of debt and preferred equity investments, low end of range			2,100,000,000
Estimated fair value of debt and preferred equity investments, high end of range			2,300,000,000
Level 1
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other assets)	0		0
Level 2
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other assets)	23,629,000		16,692,000
Level 3
Fair Value of Financial Instruments
Marketable securities	0		0
Interest rate cap and swap agreements (included in other assets)	0		0
Level 3 \| Fair Value
Fair Value of Financial Instruments
Fixed rate debt	3,840,843,000		4,421,866,000
Variable rate debt	1,673,313,000		1,612,224,000
Equity marketable securities \| Level 1
Fair Value of Financial Instruments
Marketable securities	0		0
Commercial mortgage-backed securities
Fair Value of Financial Instruments
Marketable securities	28,252,000		28,579,000
Commercial mortgage-backed securities \| Level 2
Fair Value of Financial Instruments
Marketable securities	28,252,000		28,579,000
Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017
Fair Value of Financial Instruments
Debt and preferred equity investments	250,500,000		0	$ 0
Total fixed rate \| Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017
Fair Value of Financial Instruments
Notes receivable	250,500,000
Accrued interest	7,700,000
Joint venture
Fair Value of Financial Instruments
Equity method investments	3,034,596,000		$ 2,362,989,000
919 Third Avenue \| Joint venture \| 919 Third Avenue
Fair Value of Financial Instruments
Purchase price and other fair value adjustments	$ 49,300,000

Financial Instruments: Derivatives and Hedging (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financial Instruments: Derivatives and Hedging
Fair Value	$ 23,628,000
Gain (loss) from changes in fair value	(200,000)	$ (100,000)
Fair value of derivatives in a net liability position	0
Aggregate termination value	0
Estimated current balance held in accumulated other comprehensive loss to be reclassified into earnings within the next 12 months	1,300,000
Share of joint venture of accumulated other comprehensive loss reclassified into equity in net income from unconsolidated joint ventures within the next 12 months	1,000,000
Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion)	10,595,000	(2,796,000)
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	330,000	1,378,000
Amount of (Loss) Recognized into Income (Ineffective Portion)	(98,000)	(103,000)
Interest Rate Swap Expiring in July 2023
Financial Instruments: Derivatives and Hedging
Notional Value	$ 200,000,000
Strike Rate	1.131%
Fair Value	$ 14,149,000
Interest Rate Swap Expiring in July 2023
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000,000
Strike Rate	1.161%
Fair Value	$ 6,927,000
Interest Rate Cap Expiring September 2019
Financial Instruments: Derivatives and Hedging
Notional Value	$ 137,500,000
Strike Rate	4.00%
Fair Value	$ 19,000
Interest Rate Swap Expiring November 2020
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000,000
Strike Rate	1.928%
Fair Value	$ 1,273,000
Interest Rate Swap Expiring November 2020, 2
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000,000
Strike Rate	1.934%
Fair Value	$ 1,260,000
Interest Rate Swaps/Caps
Financial Instruments: Derivatives and Hedging
Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion)	7,282,000	(3,137,000)
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	329,000	979,000
Amount of (Loss) Recognized into Income (Ineffective Portion)	(9,000)	(8,000)
Joint venture
Financial Instruments: Derivatives and Hedging
Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion)	3,313,000	341,000
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	1,000	399,000
Amount of (Loss) Recognized into Income (Ineffective Portion)	$ (89,000)	$ (95,000)

Commitments and Contingencies (Details) $ in Thousands	3 Months Ended
Commitments and Contingencies (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Initial term of non cancellable operating leases, minimum (in years)	1 year
Capital lease
Remaining 2018	$ 1,790
2019	2,411
2020	2,620
2021	2,794
2022	2,794
2023	2,794
Thereafter	817,100
Total minimum lease payments	832,303
Amount representing interest	(789,274)
Capital lease obligations	43,029
Non-cancellable operating leases
Remaining 2018	23,286
2019	31,066
2020	31,437
2021	31,628
2022	29,472
2023	27,166
Thereafter	676,088
Total minimum lease payments	$ 850,143

Segment Information - Additional Information (Details)
$ in Thousands

3 Months Ended

Mar. 31, 2018

USD ($)

segment

Mar. 31, 2017

USD ($)

Dec. 31, 2017

USD ($)

Segment information

Number of reportable segments (segment) | segment

Total revenues

$ 301,695

$ 377,381

47,449

51,320

Total assets

^[1]

13,380,870

$ 13,982,904

Marketing, general and administrative

23,528

24,143

Operating Segments | Real Estate Segment

Segment information

Total revenues

256,405

337,082

14,024

13,807

Total assets

11,144,740

11,643,261

Operating Segments | Debt and Preferred Equity Segment

Segment information

Total revenues

45,290

40,299

33,425

$ 37,513

Total assets

$ 2,236,130

$ 2,339,643

[1]

Segment Information - Schedule of Reconciliation of Income from Continuing Operations to Net Income Attributable to SL Green Common Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of income from continuing operations to net income attributable to SL Green common stockholders
Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities	$ 47,449	$ 51,320
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(6,440)	2,047
Purchase price and other fair value adjustments	49,293	0
Gain on sale of real estate, net	23,521	567
Depreciable real estate reserves	0	(56,272)
Gain on sale of investment in marketable securities	0	3,262
Net income	$ 113,823	$ 924

Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details) $ in Billions	3 Months Ended
	Mar. 31, 2018 USD ($) ft² building shares
Real estate properties
Number of Properties \| building	95
Approximate Square Feet unaudited (sqft)	32,449,593
Weighted Average Occupancy unaudited (as a percent)	91.40%
Debt and preferred equity investments including investments held by unconsolidated joint ventures \| $	$ 2.1
Debt and preferred equity investments and other financing receivables included in other balance sheet items \| $	$ 0.1
Number of shares to be received on redemption of one unit of limited partnership interests (shares) \| shares	1
Commercial properties
Real estate properties
Number of Properties \| building	82
Approximate Square Feet unaudited (sqft)	29,820,737
Weighted Average Occupancy unaudited (as a percent)	91.60%
Residential
Real estate properties
Number of Properties \| building	13
Approximate Square Feet unaudited (sqft)	2,628,856
Weighted Average Occupancy unaudited (as a percent)	88.90%
Managed office properties
Real estate properties
Approximate Square Feet unaudited (sqft)	336,000
Consolidated properties
Real estate properties
Number of Properties \| building	58
Approximate Square Feet unaudited (sqft)	16,723,494
Consolidated properties \| Commercial properties
Real estate properties
Number of Properties \| building	55
Approximate Square Feet unaudited (sqft)	16,251,389
Consolidated properties \| Residential
Real estate properties
Number of Properties \| building	3
Approximate Square Feet unaudited (sqft)	472,105
Unconsolidated properties
Real estate properties
Number of Properties \| building	37
Approximate Square Feet unaudited (sqft)	15,726,099
Unconsolidated properties \| Commercial properties
Real estate properties
Number of Properties \| building	27
Approximate Square Feet unaudited (sqft)	13,569,348
Unconsolidated properties \| Residential
Real estate properties
Number of Properties \| building	10
Approximate Square Feet unaudited (sqft)	2,156,751
Manhattan
Real estate properties
Number of Properties \| building	57
Approximate Square Feet unaudited (sqft)	26,114,537
Weighted Average Occupancy unaudited (as a percent)	92.80%
Manhattan \| Office
Real estate properties
Number of Properties \| building	31
Approximate Square Feet unaudited (sqft)	24,552,255
Weighted Average Occupancy unaudited (as a percent)	94.20%
Manhattan \| Retail
Real estate properties
Number of Properties \| building	13
Approximate Square Feet unaudited (sqft)	650,553
Weighted Average Occupancy unaudited (as a percent)	94.20%
Manhattan \| Development/Redevelopment
Real estate properties
Number of Properties \| building	11
Approximate Square Feet unaudited (sqft)	735,199
Weighted Average Occupancy unaudited (as a percent)	44.40%
Manhattan \| Fee Interest
Real estate properties
Number of Properties \| building	2
Approximate Square Feet unaudited (sqft)	176,530
Weighted Average Occupancy unaudited (as a percent)	100.00%
Manhattan \| Residential
Real estate properties
Number of Properties \| building	13
Approximate Square Feet unaudited (sqft)	2,628,856
Weighted Average Occupancy unaudited (as a percent)	88.90%
Manhattan \| Consolidated properties
Real estate properties
Number of Properties \| building	33
Approximate Square Feet unaudited (sqft)	13,185,189
Manhattan \| Consolidated properties \| Office
Real estate properties
Number of Properties \| building	20
Approximate Square Feet unaudited (sqft)	12,387,091
Manhattan \| Consolidated properties \| Retail
Real estate properties
Number of Properties \| building	4
Approximate Square Feet unaudited (sqft)	302,583
Manhattan \| Consolidated properties \| Development/Redevelopment
Real estate properties
Number of Properties \| building	8
Approximate Square Feet unaudited (sqft)	318,985
Manhattan \| Consolidated properties \| Fee Interest
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	176,530
Manhattan \| Consolidated properties \| Residential
Real estate properties
Number of Properties \| building	3
Approximate Square Feet unaudited (sqft)	472,105
Manhattan \| Consolidated properties \| Dual property type, retail portion
Real estate properties
Approximate Square Feet unaudited (sqft)	270,132
Manhattan \| Consolidated properties \| Dual property type, residential portion
Real estate properties
Approximate Square Feet unaudited (sqft)	222,855
Manhattan \| Unconsolidated properties
Real estate properties
Number of Properties \| building	24
Approximate Square Feet unaudited (sqft)	12,929,348
Manhattan \| Unconsolidated properties \| Office
Real estate properties
Number of Properties \| building	11
Approximate Square Feet unaudited (sqft)	12,165,164
Manhattan \| Unconsolidated properties \| Retail
Real estate properties
Number of Properties \| building	9
Approximate Square Feet unaudited (sqft)	347,970
Manhattan \| Unconsolidated properties \| Development/Redevelopment
Real estate properties
Number of Properties \| building	3
Approximate Square Feet unaudited (sqft)	416,214
Manhattan \| Unconsolidated properties \| Fee Interest
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	0
Manhattan \| Unconsolidated properties \| Residential
Real estate properties
Number of Properties \| building	10
Approximate Square Feet unaudited (sqft)	2,156,751
Suburban
Real estate properties
Number of Properties \| building	25
Approximate Square Feet unaudited (sqft)	3,706,200
Weighted Average Occupancy unaudited (as a percent)	83.30%
Suburban \| Office
Real estate properties
Number of Properties \| building	22
Approximate Square Feet unaudited (sqft)	3,653,200
Weighted Average Occupancy unaudited (as a percent)	83.10%
Suburban \| Retail
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	52,000
Weighted Average Occupancy unaudited (as a percent)	100.00%
Suburban \| Development/Redevelopment
Real estate properties
Number of Properties \| building	2
Approximate Square Feet unaudited (sqft)	1,000
Weighted Average Occupancy unaudited (as a percent)	0.00%
Suburban \| Residential
Real estate properties
Number of Properties \| building	0
Approximate Square Feet unaudited (sqft)	0
Weighted Average Occupancy unaudited (as a percent)	0.00%
Suburban \| Consolidated properties
Real estate properties
Number of Properties \| building	22
Approximate Square Feet unaudited (sqft)	3,066,200
Suburban \| Consolidated properties \| Office
Real estate properties
Number of Properties \| building	20
Approximate Square Feet unaudited (sqft)	3,013,200
Suburban \| Consolidated properties \| Retail
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	52,000
Suburban \| Consolidated properties \| Development/Redevelopment
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	1,000
Suburban \| Consolidated properties \| Residential
Real estate properties
Number of Properties \| building	0
Approximate Square Feet unaudited (sqft)	0
Suburban \| Unconsolidated properties
Real estate properties
Number of Properties \| building	3
Approximate Square Feet unaudited (sqft)	640,000
Suburban \| Unconsolidated properties \| Office
Real estate properties
Number of Properties \| building	2
Approximate Square Feet unaudited (sqft)	640,000
Suburban \| Unconsolidated properties \| Retail
Real estate properties
Number of Properties \| building	0
Approximate Square Feet unaudited (sqft)	0
Suburban \| Unconsolidated properties \| Development/Redevelopment
Real estate properties
Number of Properties \| building	1
Approximate Square Feet unaudited (sqft)	0
Suburban \| Unconsolidated properties \| Residential
Real estate properties
Number of Properties \| building	0
Approximate Square Feet unaudited (sqft)	0