SL Green Realty (SLG) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 08, 2019
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, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Emerging Growth Company	false
Entity Small Business	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		84,327,249
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, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Emerging Growth Company	false
Entity Small Business	false
Amendment Flag	false
Entity Common Stock, Shares Outstanding		1,022,624

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Commercial real estate properties, at cost:
Land and land interests		$ 1,775,006	$ 1,774,899
Building and improvements		5,294,612	5,268,484
Building leasehold and improvements		1,423,282	1,423,107
Right of use asset - financing leases		47,445	47,445
Right of use asset - operating leases		396,148	0
Total commercial real estate properties, at cost		8,936,493	8,513,935
Less: accumulated depreciation		(2,154,075)	(2,099,137)
Total commercial real estate properties, net		6,782,418	6,414,798
Cash and cash equivalents		144,323	129,475
Restricted cash		151,388	149,638
Investments in marketable securities		29,406	28,638
Tenant and other receivables		47,829	41,589
Related party receivables		29,458	28,033
Deferred rents receivable		337,099	335,985
Debt and preferred equity investments, net of discounts and deferred origination fees of $21,584 and $22,379 in 2019 and 2018, respectively, and allowance of $1,750 and $5,750 in 2019 and 2018, respectively.		2,272,241	2,099,393
Investments in unconsolidated joint ventures		3,055,368	3,019,020
Deferred costs, net		211,615	209,110
Other assets		324,629	295,679
Total assets	[1]	13,385,774	12,751,358
Liabilities
Mortgages and other loans payable, net		2,018,561	1,961,240
Revolving credit facility, net		782,656	492,196
Unsecured term loans, net		1,493,357	1,493,051
Unsecured notes, net		1,495,490	1,495,214
Accrued interest payable		28,930	23,154
Other liabilities		135,448	116,566
Accounts payable and accrued expenses		111,899	147,060
Deferred revenue		102,598	94,453
Lease liability - financing leases		43,823	43,616
Lease liability - operating leases		389,857	3,603
Dividend and distributions payable		80,047	80,430
Security deposits		61,139	64,688
Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities		100,000	100,000
Total liabilities	[1]	6,843,805	6,115,271
Commitments and contingencies
Noncontrolling interests in Operating Partnership		412,361	387,805
Preferred units		285,285	300,427
Equity
Series I Preferred Stock, $0.01 par value, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2019 and December 31, 2018		221,932	221,932
Common stock, $0.01 par value, 160,000 shares authorized and 84,328 and 84,739 issued and outstanding at March 31, 2019 and December 31, 2018, respectively (including 1,055 shares held in treasury at March 31, 2019 and December 31, 2018)		843	847
Additional paid-in-capital		4,492,581	4,508,685
Treasury stock at cost		(124,049)	(124,049)
Accumulated other comprehensive (loss) income		(4,005)	15,108
Retained earnings		1,210,497	1,278,998
Total SL Green stockholders' equity		5,797,799	5,901,521
Noncontrolling interests in other partnerships		46,524	46,334
Total equity		5,844,323	5,947,855
SL Green stockholders equity:
Total liabilities and equity/capital		13,385,774	12,751,358
SL Green Operating Partnership
Commercial real estate properties, at cost:
Land and land interests		1,775,006	1,774,899
Building and improvements		5,294,612	5,268,484
Building leasehold and improvements		1,423,282	1,423,107
Right of use asset - financing leases		47,445	47,445
Right of use asset - operating leases		396,148	0
Total commercial real estate properties, at cost		8,936,493	8,513,935
Less: accumulated depreciation		(2,154,075)	(2,099,137)
Total commercial real estate properties, net		6,782,418	6,414,798
Cash and cash equivalents		144,323	129,475
Restricted cash		151,388	149,638
Investments in marketable securities		29,406	28,638
Tenant and other receivables		47,829	41,589
Related party receivables		29,458	28,033
Deferred rents receivable		337,099	335,985
Debt and preferred equity investments, net of discounts and deferred origination fees of $21,584 and $22,379 in 2019 and 2018, respectively, and allowance of $1,750 and $5,750 in 2019 and 2018, respectively.		2,272,241	2,099,393
Investments in unconsolidated joint ventures		3,055,368	3,019,020
Deferred costs, net		211,615	209,110
Other assets		324,629	295,679
Total assets	[2]	13,385,774	12,751,358
Liabilities
Mortgages and other loans payable, net		2,018,561	1,961,240
Revolving credit facility, net		782,656	492,196
Unsecured term loans, net		1,493,357	1,493,051
Unsecured notes, net		1,495,490	1,495,214
Accrued interest payable		28,930	23,154
Other liabilities		135,448	116,566
Accounts payable and accrued expenses		111,899	147,060
Deferred revenue		102,598	94,453
Lease liability - financing leases		43,823	43,616
Lease liability - operating leases		389,857	3,603
Dividend and distributions payable		80,047	80,430
Security deposits		61,139	64,688
Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities		100,000	100,000
Total liabilities	[2]	6,843,805	6,115,271
Commitments and contingencies
Noncontrolling interests in Operating Partnership		412,361	387,805
Limited partner interests in SLGOP (4,261 and 4,131 limited partner common units outstanding at March 31, 2019 and December 31, 2018, respectively)		412,361	387,805
Preferred units		285,285	300,427
Equity
Accumulated other comprehensive (loss) income		(4,005)	15,108
SL Green stockholders equity:
Series I Preferred Units, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2019 and December 31, 2018		221,932	221,932
SL Green partners' capital (875 and 878 general partner common units and 82,397 and 82,806 limited partner common units outstanding at March 31, 2019 and December 31, 2018, respectively)		5,579,872	5,664,481
Total SLGOP partners' capital		5,797,799	5,901,521
Noncontrolling interests in other partnerships		46,524	46,334
Total capital		5,844,323	5,947,855
Total liabilities and equity/capital		$ 13,385,774	$ 12,751,358
[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: $110.0 million and $110.0 million of land, $0.3 billion and $0.3 billion of building and improvements, $0.0 million and $2.0 million of building and leasehold improvements, $61.1 million and $47.4 million of right of use assets, $45.0 million and $42.2 million of accumulated depreciation, $114.7 million and $112.6 million of other assets included in other line items, $140.6 million and $140.8 million of real estate debt, net, $0.4 million and $0.4 million of accrued interest payable, $56.2 million and $43.6 million of lease liabilities, and $16.5 million and $18.3 million of other liabilities included in other line items as of March 31, 2019 and December 31, 2018, 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: $110.0 million and $110.0 million of land, $0.3 billion and $0.3 billion of building and improvements, $0.0 million and $2.0 million of building and leasehold improvements, $61.1 million and $47.4 million of right of use assets, $45.0 million and $42.2 million of accumulated depreciation, $114.7 million and $112.3 million of other assets included in other line items, $140.6 million and $140.8 million of real estate debt, net, $0.4 million and $0.4 million of accrued interest payable, $56.2 million and $43.6 million of lease liabilities, and $16.5 million and $18.3 million of other liabilities included in other line items as of March 31, 2019 and December 31, 2018, respectively.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt and preferred equity investments, discount and deferred origination fees	$ 21,584	$ 22,379
Allowance for loan and lease losses, real estate	$ 1,750	$ 5,750
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)	84,328,000	84,739,000
Common stock, shares outstanding (in shares)	84,328,000	84,739,000
Treasury stock, shares (in shares)	1,055,000	1,055,000
Land and land interests	$ 1,775,006	$ 1,774,899
Building and improvements	5,294,612	5,268,484
Building leasehold and improvements	1,423,282	1,423,107
Right of use asset - financing leases	47,445	47,445
Accumulated depreciation	2,154,075	2,099,137
Other assets	324,629	295,679
Mortgages and other loans payable, net	2,018,561	1,961,240
Accrued interest payable	28,930	23,154
Lease liability - financing leases	43,823	43,616
Other liabilities	$ 135,448	$ 116,566
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	$ 25
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	$ 110,000	$ 110,000
Building and improvements	300,000	300,000
Building leasehold and improvements	0	2,000
Right of use asset - financing leases	61,100	47,400
Accumulated depreciation	45,000	42,200
Other assets	114,700	112,600
Mortgages and other loans payable, net	140,600	140,800
Accrued interest payable	400	400
Lease liability - financing leases	56,200	43,600
Other liabilities	16,500	18,300
SL Green Operating Partnership
Debt and preferred equity investments, discount and deferred origination fees	21,584	22,379
Allowance for loan and lease losses, real estate	$ 1,750	$ 5,750
Limited partner interests in Operating Partnership, limited partner common units outstanding (shares)	4,261,000	4,131,000
SL Green partner's capital, general partner common units outstanding (shares)	875,000	878,000
SL Green partners' capital, limited partner common units outstanding (shares)	82,397,000	82,806,000
Land and land interests	$ 1,775,006	$ 1,774,899
Building and improvements	5,294,612	5,268,484
Building leasehold and improvements	1,423,282	1,423,107
Right of use asset - financing leases	47,445	47,445
Accumulated depreciation	2,154,075	2,099,137
Other assets	324,629	295,679
Mortgages and other loans payable, net	2,018,561	1,961,240
Accrued interest payable	28,930	23,154
Lease liability - financing leases	43,823	43,616
Other liabilities	$ 135,448	$ 116,566
SL Green Operating Partnership | Series I Preferred Stock
Preferred units, liquidation preference (in dollars per share)	$ 25	$ 25
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	$ 110,000	$ 110,000
Building and improvements	300,000	300,000
Building leasehold and improvements	0	2,000
Right of use asset - financing leases	61,100	47,400
Accumulated depreciation	45,000	42,200
Other assets	114,700	112,300
Mortgages and other loans payable, net	140,600	140,800
Accrued interest payable	400	400
Lease liability - financing leases	56,200	43,600
Other liabilities	$ 16,500	$ 18,300

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues
Rental revenue, net	$ 240,118	$ 241,768
Investment income	50,031	45,290
Other income	14,106	14,637
Total revenues	304,255	301,695
Expenses
Operating expenses, including related party expenses of $2,793 in 2019 and $3,834 in 2018, respectively.	57,698	59,782
Real estate taxes	46,688	45,661
Operating lease rent	8,298	8,308
Interest expense, net of interest income	50,525	47,916
Amortization of deferred financing costs	2,742	3,537
Depreciation and amortization	68,343	69,388
Transaction related costs	55	162
Marketing, general and administrative	25,979	23,528
Total expenses	260,328	258,282
Equity in net (loss) income from unconsolidated joint ventures	(5,234)	4,036
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	17,166	(6,440)
Purchase price and other fair value adjustments	(2,041)	49,293
(Loss) gain on sale of real estate, net	(1,049)	23,521
Net income	52,769	113,823
Net income attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(2,278)	(5,272)
Noncontrolling interests in other partnerships	(237)	(198)
Preferred units distributions	(2,724)	(2,849)
Net income (loss) attributable to SL Green/SLGOP	47,530	105,504
Perpetual preferred stock dividends	(3,738)	(3,738)
Net income attributable to SL Green common stockholders	$ 43,792	$ 101,766
Basic Earnings per Share (usd per share)	$ 0.52	$ 1.12
Diluted Earnings per Share (usd per share)	$ 0.52	$ 1.12
Basic weighted average common shares outstanding (in shares)	83,313	90,520
Diluted weighted average common shares and common share equivalents outstanding (in shares)	87,810	95,256
Diluted weighted average common units and common unit equivalents outstanding (in shares)	87,810	95,256
SL Green Operating Partnership
Revenues
Rental revenue, net	$ 240,118	$ 241,768
Investment income	50,031	45,290
Other income	14,106	14,637
Total revenues	304,255	301,695
Expenses
Operating expenses, including related party expenses of $2,793 in 2019 and $3,834 in 2018, respectively.	57,698	59,782
Real estate taxes	46,688	45,661
Operating lease rent	8,298	8,308
Interest expense, net of interest income	50,525	47,916
Amortization of deferred financing costs	2,742	3,537
Depreciation and amortization	68,343	69,388
Transaction related costs	55	162
Marketing, general and administrative	25,979	23,528
Total expenses	260,328	258,282
Equity in net (loss) income from unconsolidated joint ventures	(5,234)	4,036
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	17,166	(6,440)
Purchase price and other fair value adjustments	(2,041)	49,293
(Loss) gain on sale of real estate, net	(1,049)	23,521
Net income	52,769	113,823
Net income attributable to noncontrolling interests:
Noncontrolling interests in the Operating Partnership	(2,278)
Noncontrolling interests in other partnerships	(237)	(198)
Preferred units distributions	(2,724)	(2,849)
Net income (loss) attributable to SL Green/SLGOP	49,808	110,776
Perpetual preferred unit distributions	(3,738)	(3,738)
Net income attributable to SLGOP common unitholders	$ 46,070	$ 107,038
Basic Earnings per Unit (usd per share)	$ 0.52	$ 1.12
Diluted Earnings per Unit (usd per share)	$ 0.52	$ 1.12
Basic weighted average common shares outstanding (in shares)	87,646	95,203
Diluted weighted average common units and common unit equivalents outstanding (in shares)	87,810	95,256

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating expenses, paid to related parties	$ 2,793	$ 3,834
SL Green Operating Partnership
Operating expenses, paid to related parties	$ 2,793	$ 3,834

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net income	$ 52,769	$ 113,823
Other comprehensive (loss) income:
Change in net unrealized gain (loss) on derivative instruments, including SL Green's/SLGOP's share of joint venture net unrealized (loss) gain on derivative instruments	(20,884)	10,913
Change in unrealized gain (loss) on marketable securities	768	(325)
Other comprehensive (loss) income	(20,116)	10,588
Comprehensive income	32,653	124,411
Net income attributable to noncontrolling interests and preferred units distributions	(5,239)	(8,319)
Net income attributable to noncontrolling interests	(237)	(198)
Other comprehensive loss (income) attributable to noncontrolling interests	1,003	(619)
Comprehensive income attributable to SL Green/SLGOP	28,417	115,473
SL Green Operating Partnership
Net income	52,769	113,823
Other comprehensive (loss) income:
Change in net unrealized gain (loss) on derivative instruments, including SL Green's/SLGOP's share of joint venture net unrealized (loss) gain on derivative instruments	(20,884)	10,913
Change in unrealized gain (loss) on marketable securities	768	(325)
Other comprehensive (loss) income	(20,116)	10,588
Comprehensive income	32,653	124,411
Net income attributable to noncontrolling interests	(237)	(198)
Other comprehensive loss (income) attributable to noncontrolling interests	1,003	(619)
Comprehensive income attributable to SL Green/SLGOP	$ 33,419	$ 123,594

Consolidated Statement of Equit

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 (Loss)	Retained Earnings	Noncontrolling Interests	Series I Preferred StockPreferred Stock
Beginning Balance at Dec. 31, 2017	$ 6,589,454	$ 221,932	$ 939	$ 4,968,338	$ (124,049)	$ 18,604	$ 1,139,329	$ 364,361
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 of forfeitures and tax withholdings (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 (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
Beginning Balance at Dec. 31, 2017	6,589,454	221,932	$ 939	4,968,338	(124,049)	18,604	1,139,329	364,361
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
Ending Balance at Jun. 30, 2018	5,844,323	$ 221,932	$ 843	4,492,581	(124,049)	(4,005)	1,210,497	46,524
Ending Balance (in shares) at Jun. 30, 2018			83,272
Beginning Balance at Dec. 31, 2018	5,947,855		$ 847	4,508,685	$ (124,049)	15,108	1,278,998	46,334	$ 221,932
Beginning Balance (in shares) at Dec. 31, 2018			83,684
Increase (Decrease) in Stockholders' Equity
Net income	47,767						47,530	237
Other comprehensive income	(19,113)					(19,113)
Preferred dividends	(3,738)						(3,738)
DRSPP proceeds (in shares)			1
DRSPP proceeds	47			47
Conversion of units of the Operating Partnership to common stock (in shares)			5
Conversion of units in the Operating Partnership for common stock	446			446
Reallocation of noncontrolling interest in the Operating Partnership	(28,932)						(28,932)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)			(20)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	4,835			4,835
Repurchases of common stock (in shares)			(398)
Repurchases of common stock	(34,243)		$ (4)	$ (21,432)			(12,807)
Contributions to consolidated joint venture interests	161							161
Cash distributions to noncontrolling interests	(208)							$ (208)
Cash distributions declared (per common share, none of which represented a return of capital for federal income tax purposes)	(70,554)						$ (70,554)
Ending Balance at Mar. 31, 2019	$ 5,844,323					$ (4,005)

Consolidated Statement of Equ_2

Consolidated Statement of Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash distribution declared, per common share (in dollars per share)	$ 0.85	$ 0.8125

Consolidated Statement of Capit

Consolidated Statement of Capital (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jun. 30, 2018	Jan. 01, 2018
Increase (Decrease) in Partner's Capital
DRSPP proceeds	$ 47	$ 42
Conversion of common units	446
Reallocation of noncontrolling interests in the operating partnership	(28,932)	3,645
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	4,835	3,102
Repurchases of common stock	(34,243)	(354,744)
Contribution to consolidated joint venture interests	161	157
Deconsolidation of partially owned entity		(314,596)
Cash distributions to noncontrolling interests	$ (208)	$ (276)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)	1	1
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)	(20)	(19)
Repurchases of common stock (in shares)	(398)	(3,654)
Repurchases of common stock	$ (4)	$ (37)
Contributions - proceeds from stock options exercised (in shares)		4
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Contribution to consolidated joint venture interests	161	$ 157
Deconsolidation of partially owned entity		(314,596)
Cash distributions to noncontrolling interests	(208)	(276)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning Balance	5,947,855	6,589,454	$ 6,589,454
Adjusted Balance		7,159,978	7,159,978
Net income		105,702	47,767
Other comprehensive income		9,969	(19,113)
Preferred distributions		(3,738)	(3,738)
DRSPP proceeds		42	47
Conversion of common units			446
Reallocation of noncontrolling interests in the operating partnership		3,645	(28,932)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings		3,102	4,835
Repurchases of common stock		(354,744)	(34,243)
Contribution to consolidated joint venture interests		157	161
Deconsolidation of partially owned entity		(314,596)
Contributions - proceeds from stock options exercised		729
Cash distributions to noncontrolling interests		(276)	(208)
Cash distributions declared (per common unit, none of which represented a return of capital for federal income tax purposes)		(72,341)	(70,554)
Ending Balance	5,844,323	6,537,629	5,844,323
SL Green Operating Partnership | Common Stock | Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 5,664,481	$ 5,984,557	$ 5,984,557
Beginning Balance (units)	83,684	92,803	92,803
Adjusted Balance		$ 6,555,081	$ 6,555,081
Net income	$ 47,530	105,504
Preferred distributions		$ (3,738)	$ (3,738)
DRSPP proceeds (in shares)		1	1
DRSPP proceeds		$ 42	$ 47
Conversion of common units (in shares)			5
Conversion of common units			$ 446
Reallocation of noncontrolling interests in the operating partnership		$ 3,645	$ (28,932)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)		(19)	(20)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings		$ 3,102	$ 4,835
Repurchases of common stock (in shares)		(3,654)	(398)
Repurchases of common stock		$ 354,744	$ (34,243)
Contributions - proceeds from stock options exercised (in shares)		4
Contributions - proceeds from stock options exercised		$ 729
Cash distributions declared (per common unit, none of which represented a return of capital for federal income tax purposes)		(72,341)	(70,554)
Ending Balance		$ 6,237,280	$ 5,579,872
Ending Balance (units)		89,135	83,272
SL Green Operating Partnership | Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning Balance	15,108	$ 18,604	$ 18,604
Adjusted Balance		18,604	18,604
Other comprehensive income		9,969	(19,113)
Ending Balance		28,573	(4,005)
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning Balance	46,334	364,361	364,361
Adjusted Balance		364,361	364,361
Net income	237	198
Contribution to consolidated joint venture interests		157	161
Deconsolidation of partially owned entity		(314,596)
Cash distributions to noncontrolling interests		(276)	(208)
Ending Balance		49,844	46,524
Series I Preferred Stock | SL Green Operating Partnership | Preferred Units
Increase (Decrease) in Partner's Capital
Beginning Balance	$ 221,932	221,932	221,932
Adjusted Balance		221,932	221,932
Ending Balance		$ 221,932	$ 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 Cap_2

Consolidated Statement of Capital (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash distribution declared, per common share (in dollars per share)	$ 0.85	$ 0.8125
SL Green Operating Partnership
Cash distribution declared, per common share (in dollars per share)	$ 0.85	$ 0.8125

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Operating Activities
Net income	$ 52,769	$ 113,823
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	71,085	72,925
Equity in net loss (income) from unconsolidated joint ventures	5,234	(4,036)
Distributions of cumulative earnings from unconsolidated joint ventures	425	7,510
Equity in net (gain) loss on sale of interest in unconsolidated joint venture interest/real estate	(17,166)	6,440
Purchase price and other fair value adjustments	2,041	(49,293)
Loss (gain) on sale of real estate, net	1,049	(23,521)
Loan loss reserves and other investment reserves, net of recoveries	0		$ 6,839
Deferred rents receivable	(1,114)	(3,120)
Other non-cash adjustments	9,542	12,155
Changes in operating assets and liabilities:
Tenant and other receivables	(4,759)	(1,847)
Related party receivables	(1,270)	(4,567)
Deferred lease costs	(13,111)	(7,679)
Other assets	(40,218)	(47,826)
Accounts payable, accrued expenses, other liabilities and security deposits	(12,915)	18,890
Deferred revenue and land leases payable	10,721	4,692
Net cash provided by operating activities	62,313	94,546
Investing Activities
Acquisitions of real estate property	0	(1,276)
Additions to land, buildings and improvements	(39,524)	(51,631)
Acquisition deposits and deferred purchase price	(4,910)	(3,020)
Investments in unconsolidated joint ventures	(73,351)	(51,158)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	23,664	142,694
Net proceeds from disposition of real estate/joint venture interest	14,489	409,867
Other investments	(1,056)	(21,687)
Origination of debt and preferred equity investments	(430,034)	(229,428)
Repayments or redemption of debt and preferred equity investments	218,879	261,641
Net cash (used in) provided by investing activities	(291,843)	456,002
Financing Activities
Proceeds from mortgages and other loans payable	109,872	99,115
Repayments of mortgages and other loans payable	(1,127)	(9,406)
Proceeds from revolving credit facility and senior unsecured notes	520,000	455,000
Repayments of revolving credit facility and senior unsecured notes	(230,000)	(495,000)
Proceeds from stock options exercised and DRSPP issuance	47	771
Repurchase of common stock	(34,243)	(382,679)
Redemption of preferred units	(15,142)	(150)
Redemption of OP units	(15,697)	0
Distributions to noncontrolling interests in other partnerships	(208)	(276)
Contributions from noncontrolling interests in other partnerships	161	157
Distributions to noncontrolling interests in the Operating Partnership	(3,643)	(3,841)
Dividends / Distributions paid on common and preferred stock / units	(77,399)	(81,729)
Tax withholdings related to restricted share awards	(3,126)	(3,842)
Deferred loan costs and capitalized lease obligation	(3,367)	(429)
Net cash provided by (used in) financing activities	246,128	(422,309)
Net increase in cash, cash equivalents, and restricted cash	16,598	128,239
Cash, cash equivalents, and restricted cash at end of period	295,711	378,265
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership	0	15,448
Conversion of units in the Operating Partnership for common stock	446	0
Tenant improvements and capital expenditures payable	9,350	15,952
Fair value adjustment to noncontrolling interest in Operating Partnership	28,932	3,645
Deconsolidation of subsidiaries	0	298,403
Deferred leasing payable	0	1,203
Removal of fully depreciated commercial real estate properties	4,012	106,142
Share repurchase payable	0	27,935
Recognition of right of use assets and related lease liabilities	389,120	0
Amortization of lease liabilities	3,367	0
Cash and cash equivalents				$ 144,323	$ 129,475	$ 288,808
Restricted cash				151,388	149,638	89,457
Total cash, cash equivalents, and restricted cash	295,711	378,265		295,711		378,265
SL Green Operating Partnership
Operating Activities
Net income	52,769	113,823
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	71,085	72,925
Equity in net loss (income) from unconsolidated joint ventures	5,234	(4,036)
Distributions of cumulative earnings from unconsolidated joint ventures	425	7,510
Equity in net (gain) loss on sale of interest in unconsolidated joint venture interest/real estate	(17,166)	6,440
Purchase price and other fair value adjustments	2,041	(49,293)
Loss (gain) on sale of real estate, net	1,049	(23,521)
Deferred rents receivable	(1,114)	(3,120)
Other non-cash adjustments	9,542	12,155
Changes in operating assets and liabilities:
Tenant and other receivables	(4,759)	(1,847)
Related party receivables	(1,270)	(4,567)
Deferred lease costs	(13,111)	(7,679)
Other assets	(40,218)	(47,826)
Accounts payable, accrued expenses, other liabilities and security deposits	(12,915)	18,890
Deferred revenue and land leases payable	10,721	4,692
Net cash provided by operating activities	62,313	94,546
Investing Activities
Acquisitions of real estate property	0	(1,276)
Additions to land, buildings and improvements	(39,524)	(51,631)
Acquisition deposits and deferred purchase price	(4,910)	(3,020)
Investments in unconsolidated joint ventures	(73,351)	(51,158)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	23,664	142,694
Net proceeds from disposition of real estate/joint venture interest	14,489	409,867
Other investments	(1,056)	(21,687)
Origination of debt and preferred equity investments	(430,034)	(229,428)
Repayments or redemption of debt and preferred equity investments	218,879	261,641
Net cash (used in) provided by investing activities	(291,843)	456,002
Financing Activities
Proceeds from mortgages and other loans payable	109,872	99,115
Repayments of mortgages and other loans payable	(1,127)	(9,406)
Proceeds from revolving credit facility and senior unsecured notes	520,000	455,000
Repayments of revolving credit facility and senior unsecured notes	(230,000)	(495,000)
Proceeds from stock options exercised and DRSPP issuance	47	771
Repurchase of common stock	(34,243)	(382,679)
Redemption of preferred units	(15,142)	(150)
Redemption of OP units	(15,697)	0
Distributions to noncontrolling interests in other partnerships	(208)	(276)
Contributions from noncontrolling interests in other partnerships	161	157
Dividends / Distributions paid on common and preferred stock / units	(81,042)	(85,570)
Tax withholdings related to restricted share awards	(3,126)	(3,842)
Deferred loan costs and capitalized lease obligation	(3,367)	(429)
Net cash provided by (used in) financing activities	246,128	(422,309)
Net increase in cash, cash equivalents, and restricted cash	16,598	128,239
Cash, cash equivalents, and restricted cash at beginning of year	279,113	250,026	250,026
Cash, cash equivalents, and restricted cash at end of period	295,711	378,265	279,113
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership	0	15,448
Conversion of units in the Operating Partnership for common stock	446	0
Tenant improvements and capital expenditures payable	9,350	15,952
Fair value adjustment to noncontrolling interest in Operating Partnership	28,932	3,645
Deconsolidation of subsidiaries	0	298,403
Removal of fully depreciated commercial real estate properties	4,012	106,142
Share repurchase payable	0	27,935
Recognition of right of use assets and related lease liabilities	389,120	0
Amortization of lease liabilities	3,367	0
Cash and cash equivalents				144,323	129,475	288,808
Restricted cash				151,388	149,638	89,457
Total cash, cash equivalents, and restricted cash	$ 279,113	$ 250,026	$ 250,026	$ 295,711	$ 279,113	$ 378,265

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	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, 2019 , noncontrolling investors held, in the aggregate, a 4.87% 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." As of March 31, 2019 , 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 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 11,676,183 31 24,063,274 94.0 % Retail 7 (2) 325,648 7 283,832 14 609,480 98.9 % Development/Redevelopment 5 486,101 1 — 6 486,101 40.6 % Fee Interest — — 1 — 1 — — % 32 13,198,840 20 11,960,015 52 25,158,855 93.1 % Suburban Office 13 2,295,200 — — 13 2,295,200 90.4 % Retail 1 52,000 — — 1 52,000 100.0 % Development/Redevelopment 1 1,000 — — 1 1,000 — % 15 2,348,200 — — 15 2,348,200 90.6 % Total commercial properties 47 15,547,040 20 11,960,015 67 27,507,055 92.9 % Residential: Manhattan Residential 2 (2) 445,105 9 2,075,896 11 2,521,001 93.3 % Suburban Residential — — — — — — — % Total residential properties 2 445,105 9 2,075,896 11 2,521,001 93.3 % Total portfolio 49 15,992,145 29 14,035,911 78 30,028,056 93.0 % (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, 2019 , 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. As of March 31, 2019 , we also managed two office buildings owned by third parties encompassing approximately 2.1 million square feet (unaudited), and held debt and preferred equity investments with a book value of $2.3 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, 2019 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, 2019 . 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, 2018 of the Company and the Operating Partnership. The consolidated balance sheet at December 31, 2018 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.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	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 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. The Company classifies those leases under which the Company is the lessee at lease commencement as finance or operating leases. Leases qualify as finance leases if the lease transfers ownership of the asset at the end of the lease term, the lease grants an option to purchase the asset that we are reasonably certain to exercise, the lease term is for a major part of the remaining economic life of the asset, or the present value of the lease payments exceeds substantially all of the fair value of the asset. Leases that do not qualify as finance leases are deemed to be operating leases. At lease commencement the Company records a lease liability which is measured as the present value of the lease payments and a right of use asset which is measured as the amount of the lease liability and any initial direct costs incurred. The Company applies a discount rate to determine the present value of the lease payments. If the rate implicit in the lease is known, the Company uses that rate. If the rate implicit in the lease is not known, the Company uses a discount rate reflective of the Company’s collateralized borrowing rate given the term of the lease. To determine the discount rate, the Company employs a third party specialist to develop a curve based primarily on the observable borrowing rates of the Company, other REITs, and other corporate borrowers with long-term borrowings. On the statements of operations, operating leases are expensed through operating lease rent while financing leases are expensed through amortization and interest expense. On the balance sheet, financing leases include the amounts previously captioned "Properties under capital lease." When applicable, the Company combines the consideration for lease and non-lease components in the calculation of the value of the lease obligation and right-of-use asset. On a periodic basis, we assess whether there are any indications that the value of our real estate properties may be 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 and depreciation expense is no longer recorded. We recognized $1.2 million and $2.4 million of rental revenue for the three months ended March 31, 2019 and 2018 , 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. 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, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Identified intangible assets (included in other assets): Gross amount $ 266,540 $ 266,540 Accumulated amortization (244,246 ) (241,040 ) Net (1) $ 22,294 $ 25,500 Identified intangible liabilities (included in deferred revenue): Gross amount $ 276,245 $ 276,245 Accumulated amortization (256,010 ) (253,767 ) Net (1) $ 20,235 $ 22,478 (1) As of March 31, 2019 , and December 31, 2018 , no net intangible assets and no 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 security as held-to-maturity, available-for-sale, or trading. As of March 31, 2019 , we did not have any securities designated as held-to-maturity or trading. We account for our available-for-sale 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. The cost of marketable securities sold and the amount reclassified out of accumulated other comprehensive income into earnings is determined using the specific identification method. Any unrealized losses that are determined to be other-than-temporary are recognized in earnings up to their credit component. At March 31, 2019 and December 31, 2018 , we held the following marketable securities (in thousands): March 31, 2019 December 31, 2018 Commercial mortgage-backed securities $ 29,406 $ 28,638 Total marketable securities available-for-sale $ 29,406 $ 28,638 The cost basis of the commercial mortgage-backed securities was $27.5 million at both March 31, 2019 and December 31, 2018 . These securities mature at various times through 2035. We held no equity marketable securities as of March 31, 2019 and December 31, 2018 . During the three months ended March 31, 2019 , we did not dispose of any marketable securities. During the three months ended March 31, 2018 , we did not dispose of any marketable securities. 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, 2019 . Deferred Lease Costs Deferred lease costs consist of incremental fees and direct costs that would not have been incurred if the lease had not been obtained and are amortized on a straight-line basis over the related lease term. Lease Classification Lease classification for leases under which the Company is the lessor is evaluated at lease commencement and leases not classified as sales-type leases or direct financing leases are classified as operating leases. Leases qualify as sales-type leases if the contract includes either transfer of ownership clauses, certain purchase options, a lease term representing a major part of the economic life of the asset, or the present value of the lease payments and residual guarantees provided by the lessee exceeds substantially all of the fair value of the asset. Additionally, leasing an asset so specialized that it is not deemed to have any value to the Company at the end of the lease term may also trigger sales-type lease classification. Leases would qualify as direct financing leases when the present value of the lease payments and residual value guarantees provided by the lessee and unrelated third parties exceeds substantially all of the fair value of the asset and collection of the payments is probable. Revenue Recognition Rental revenue for operating leases is recognized on a straight-line basis over the term of the lease. Rental revenue recognition commences when the tenant takes possession or controls the physical use of the leased space. In order for the tenant to take possession, the leased space must be substantially ready for its intended use. To determine whether the leased space is substantially ready for its intended use, management evaluates whether we are or the tenant is the owner of tenant improvements for accounting purposes. When management concludes that we are the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of the finished space, which is when such tenant improvements are substantially complete. In certain instances, when management concludes that we are not the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of or controls the space. When management concludes that we are the owner of tenant improvements for accounting purposes, we record amounts funded to construct the tenant improvements as a capital asset. For these tenant improvements, we record amounts reimbursed by tenants as a reduction of the capital asset. When management concludes that the tenant is the owner of tenant improvements for accounting purposes, we record our contribution towards those improvements as a lease incentive, which is included in deferred costs, net on our consolidated balance sheets and amortized as a reduction to rental revenue on a straight-line basis over the term of the lease. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rents receivable on the consolidated balance sheets. In addition to base rent, our tenants also generally will pay variable rent which represents their pro rata share of increases in real estate taxes and operating expenses for the building over a base year. In some leases, in lieu of paying additional rent based upon increases in building operating expenses, the tenant will pay additional rent based upon increases in the wage rate paid to porters over the porters' wage rate in effect during a base year or increases in the consumer price index over the index value in effect during a base year. In addition, many of our leases contain fixed percentage increases over the base rent to cover escalations. Electricity is most often supplied by the landlord either on a sub-metered basis, or rent inclusion basis (i.e., a fixed fee is included in the rent for electricity, which amount may increase based upon increases in electricity rates or increases in electrical usage by the tenant). Base building services other than electricity (such as heat, air conditioning and freight elevator service during business hours, and base building cleaning) are typically provided at no additional cost, with the tenant paying additional rent only for services which exceed base building services or for services which are provided outside normal business hours. These escalations are based on actual expenses incurred in the prior calendar year. If the expenses in the current year are different from those in the prior year, then during the current year, the escalations will be adjusted to reflect the actual expenses for the current year. Rental revenue is recognized if collectability is probable. If collectability of substantially all of the lease payments is assessed as not probable, any difference between the rental revenue recognized to date and the lease payments that have been collected is recognized as a current-period adjustment to rental revenue. A subsequent change in the assessment of collectability to probable may result in a current-period adjustment to rental revenue for any difference between the rental revenue that would have been recognized if collectability had always been assessed as probable and the rental revenue recognized to date. The Company provides its tenants with certain customary services for lease contracts such as common area maintenance, general security or snow removal. We have elected to combine the nonlease components with the lease components of our operating lease agreements and account for them as a single lease component in accordance with ASC 842. We record a gain on sale of real estate assets when we no longer hold a controlling financial interest in the entity holding the real estate, a contract exists with a third party and that third party has control of the assets acquired. Investment income on debt and preferred equity investments is accrued based on the contractual terms of the instruments and when, in the opinion of management, it is deemed collectible. Some debt and preferred equity investments provide for accrual of interest at specified rates, which differ from current payment terms. Interest is recognized on such loans at the accrual rate subject to management's determination that accrued interest is ultimately collectible, based on the underlying collateral and operations of the borrower. If management cannot make this determination, interest income above the current pay rate is recognized only upon actual receipt. Deferred origination fees, original issue discounts and loan origination costs, if any, are recognized as an adjustment to interest income over the terms of the related investments using the effective interest method. Fees received in connection with loan commitments are also deferred until the loan is funded and are then recognized over the term of the loan as an adjustment to yield. Discounts or premiums associated with the purchase of loans are amortized or accreted into interest income as a yield adjustment on the effective interest method based on expected cash flows through the expected maturity date of the related investment. If we purchase a debt or preferred equity investment at a discount, intend to hold it until maturity and expect to recover the full value of the investment, we accrete the discount into income as an adjustment to yield over the term of the investment. If we purchase a debt or preferred equity investment at a discount with the intention of foreclosing on the collateral, we do not accrete the discount. For debt investments acquired at a discount for credit quality, the difference between contractual cash flows and expected cash flows at acquisition is not accreted. Anticipated exit fees, the collection of which is expected, are also recognized over the term of the loan as an adjustment to yield. Debt and preferred equity investments are placed on a non-accrual status at the earlier of the date at which payments become 90 days past due or when, in the opinion of management, a full recovery of interest income becomes doubtful. Interest income recognition on any non-accrual debt or preferred equity investment is resumed when such non-accrual debt or preferred equity investment becomes contractually current and performance is demonstrated to be resumed. Interest is recorded as income on impaired loans only to the extent cash is received. We may syndicate a portion of the loans that we originate or sell the loans individually. When a transaction meets the criteria for sale accounting, we recognize gain or loss based on the difference between the sales price and the carrying value of the loan sold. Any related unamortized deferred origination fees, original issue discounts, loan origination costs, discounts or premiums at the time of sale are recognized as an adjustment to the gain or loss on sale, which is included in investment income on the consolidated statement of operations. Any fees received at the time of sale or syndication are recognized as part of investment income. Asset management fees are recognized on a straight-line basis over the term of the asset management agreement. Allowance for Loan Loss and Other Investment Reserves The expense for loan loss and other investment reserves in connection with debt and preferred equity investments is the charge to earnings to adjust the allowance for possible losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. The Company evaluates debt and preferred equity investments that are classified as held to maturity for possible impairment or credit deterioration associated with the performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower/sponsor. Quarterly, the Company assigns each loan a risk rating. Based on a 3-point scale, loans are rated “1” through “3,” from less risk to greater risk, which ratings are defined as follows: 1 - Low Risk Assets - Low probability of loss, 2 - Watch List Assets - Higher potential for loss, 3 - High Risk Assets - Loss more likely than not. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired. 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. Debt and preferred equity investments that are classified as 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. We have elected, and may elect in the future, to treat certain of our 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, 2019 , we recorded Federal, state and local tax provisions of $0.8 million . 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. The Tax Act has not had a material impact on our financial statements for the three months ended March 31, 2019 . 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, 2019 . For the three months ended March 31, 2019 , the following properties contributed more than 5.0% of our annualized cash rent, including our share of joint venture annualized cash rent: Property Three Months Ended March 31, 2019 11 Madison Avenue 7.4% 1185 Avenue of the Americas 6.7% 420 Lexington Avenue 6.3% 1515 Broadway 6.0% One Madison Avenue 5.8% Annualized cash rent for each of our 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 August 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-15, Intangibles - Goodwill and Other- Internal-Use Software (Topic 350-40), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. The amendments provide guidance on accounting for fees paid when the arrangement includes a software license and align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing costs to develop or obtain internal-use software. The guidance is effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted. 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 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This amendment removed, modified and added the disclosure requirements under Topic 820. The changes are effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted for the removed or modified disclosures with adoption of the additional disclosures upon the effective date. 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 June 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting. This amendment provides additional guidance related to share-based payment transactions for acquiring goods or services from nonemployees. The Company adopted this guidance on January 1, 2019 and it did not have a material impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities, and in July 2018, the FASB issued ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The amendments in the new standards will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standards 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 adopted this guidance on January 1, 2019, and it did not have a material impact on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and in November 2018 issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses. 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’s DPE portfolio and financing lease assets will be subject to this guidance once the Company adopts it. ASU No. 2018-19 excludes operating lease receivables from the scope of this guidance. The Company continues to evaluate 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. In July 2018, the FASB issued ASU No. 2018-10 - Codification Improvements to Topic 842, Leases, and ASU No. 2018-11 - Targeted Improvements. In December 2018, the FASB issued ASU No. 2018-20 - Narrow-Scope Improvements for Lessors and in March 2019 issued ASU No. 2019-01 - Codification Improvements. The Company adopted this guidance on January 1, 2019 using the modified retrospective approach which allows the Company to apply the guidance for the current year presentation and not adjust the prior year numbers. The Company elected the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. The new guidance applies to the ground leases under which the Company is a lessee. The Company has recognized a new asset and liability - “Right of use asset - operating leases” and “Lease liability - operating leases” - for those leases classified as operating leases under the previous standard. The Company will continue to recognize expense on a straight-line basis for these operating leases. The ground leases that the Company historically reported as “Properties under capital leases” and “Capitalized lease obligations” are now labeled “Right of use asset - financing leases” and “Lease liability - financing leases”. The expense recognition of these leases has not changed. The Company adopted the practical expedient offered in ASU No. 2018-11 that allows lessors to not separate non-lease components from the related lease components under certain conditions. In doing so, the Company has collapsed the line “Escalation and reimbursement revenues” into the “Rental revenue, net” line to reflect adopting this practical expedient. The Company also collapsed the prior year balances to conform to the current year presentation. For future leases, the Company no longer capitalizes internal leasing costs that are not incremental as defined under the new guidance. The Company has recorded an additional expense of approximately $2.2 million related to this change for the first quarter.

Property Acquisitions

Property Acquisitions	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Property Acquisitions	Property Acquisitions During the three months ended March 31, 2019 , we did not acquire any properties from a third party. In April 2019, we accepted an assignment of the equity interests in the property located at 106 Spring Street in Manhattan, in lieu of repayment of the Company's debt investment, and recorded the assets received and liabilities assumed at fair value.

Properties Held for Sale and Pr

Properties Held for Sale and Property Dispositions	3 Months Ended
	Mar. 31, 2019
Discontinued Operations and Disposal Groups [Abstract]
Properties Held for Sale and Property Dispositions	Properties Held for Sale and Property Dispositions Properties Held for Sale As of March 31, 2019 , no properties were classified as held for sale. Property Dispositions During the three months ended March 31, 2019 , we did not sell any properties to a third party.

Debt and Preferred Equity Inves

Debt and Preferred Equity Investments	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Debt and Preferred Equity Investments	Debt and Preferred Equity Investments Below is a summary of the activity relating to our debt and preferred equity investments for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of year (1) $ 2,099,393 $ 2,114,041 Debt investment originations/accretion (2) 436,819 834,304 Preferred equity investment originations/accretion (2) 3,416 151,704 Redemptions/sales/syndications/amortization (3) (271,387 ) (994,906 ) Net change in loan loss reserves 4,000 (5,750 ) Balance at end of period (1) $ 2,272,241 $ 2,099,393 (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, but did not meet the conditions for sale accounting, are included in other assets and other liabilities on the consolidated balance sheets. The following table is a rollforward of our total loan loss reserves for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of year $ 5,750 $ — Expensed — 6,839 Recoveries — — Charge-offs and reclassifications (4,000 ) (1,089 ) Balance at end of period $ 1,750 $ 5,750 At March 31, 2019 , all debt and preferred equity investments were performing in accordance with the terms of the relevant investments, with the exception of one mezzanine loan which is in maturity default as discussed in subnote 5 of the Debt Investments table below. At December 31, 2018 , all debt and preferred equity investments were performing in accordance with the terms of the relevant investments. At March 31, 2019 , the Company's loan loss reserves of $1.8 million were attributable to one investment with an unpaid principal balance of $144.8 million that is being marketed for sale, is performing in accordance with its respective terms, and was not put on nonaccrual. We have determined that we have one portfolio segment of financing receivables at March 31, 2019 and December 31, 2018 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 $89.6 million and $88.8 million at March 31, 2019 and December 31, 2018 , respectively. No financing receivables were 90 days past due at March 31, 2019 and December 31, 2018 with the exception of a $28.4 million financing receivable which was put on nonaccrual in August 2018 as a result of interest default. The loan was evaluated in accordance with our loan review procedures and the Company concluded that the fair value of the collateral exceeded the carrying amount of the loan. As of March 31, 2019 , Management estimated the weighted average risk rating for our debt and preferred equity investments to be 1.3 . Debt Investments As of March 31, 2019 and December 31, 2018 , we held the following debt investments with an aggregate weighted average current yield of 8.79% at March 31, 2019 (dollars in thousands): Loan Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Maturity (2) Fixed Rate Investments: Mezzanine Loan (3a) $ — $ 1,163,005 $ 215,511 $ 213,185 March 2020 Loan Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Maturity (2) Mezzanine Loan — 15,000 3,500 3,500 September 2021 Mezzanine Loan — 147,000 24,937 24,932 April 2022 Mezzanine Loan — 280,000 37,099 36,585 August 2022 Mezzanine Loan — 318,078 202,184 — June 2023 Mezzanine Loan — 85,097 12,708 12,706 November 2023 Mezzanine Loan — 180,000 30,000 30,000 December 2023 Mezzanine Loan (3b) — 115,000 12,943 12,941 June 2024 Mezzanine Loan — 95,000 30,000 30,000 January 2025 Mezzanine Loan — 1,712,750 55,250 55,250 June 2027 Mezzanine Loan (4) — — — 11,000 Total fixed rate $ — $ 4,110,930 $ 624,132 $ 430,099 Floating Rate Investments: Mezzanine Loan (5) — 45,025 37,500 37,499 January 2019 Mezzanine Loan (3c)(6) — 150,000 15,381 15,333 April 2019 Mezzanine Loan (3d)(6) — — 14,869 14,822 April 2019 Mezzanine Loan (6) — 40,000 19,999 19,986 April 2019 Mezzanine Loan (7) — 265,000 24,993 24,961 April 2019 Mortgage/Jr. Mortgage Participation Loan 39,321 236,424 85,308 84,012 August 2019 Mortgage/Mezzanine Loan — — 19,999 19,999 August 2019 Mortgage/Mezzanine Loan 1,027 — 128,560 154,070 September 2019 Mezzanine Loan — 350,000 34,923 34,886 October 2019 Mortgage/Mezzanine Loan 9,656 64,521 112,886 62,493 January 2020 Mezzanine Loan 509 576,313 94,118 79,164 January 2020 Mortgage/Mezzanine Loan — — 69,310 — March 2020 Mortgage Loan 9,776 — 89,995 88,501 February 2020 Mezzanine Loan 828 324,989 53,917 53,402 March 2020 Mortgage/Mezzanine Loan 8,093 — 230,879 277,694 April 2020 Mortgage/Mezzanine Loan — 62,957 36,991 37,094 June 2020 Mezzanine Loan 7,392 39,649 13,145 12,627 July 2020 Mortgage/Mezzanine Loan — — 83,663 83,449 October 2020 Mezzanine Loan 35,467 375,459 92,055 88,817 November 2020 Mortgage and Mezzanine Loan 31,027 — 101,028 98,804 December 2020 Mortgage and Mezzanine Loan — — 35,295 35,266 December 2020 Jr. Mortgage Participation/Mezzanine Loan — 60,000 15,674 15,665 July 2021 Mezzanine Loan (8) — — — 7,305 Mezzanine Loan (8) — — — 14,998 Mezzanine Loan (8) — — — 21,990 Total floating rate $ 143,096 $ 2,590,337 $ 1,410,488 $ 1,382,837 Total $ 143,096 $ 6,701,267 $ 2,034,620 $ 1,812,936 (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) 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 , and (d) $14.1 million . (4) This loan was sold in 2019. (5) As of January 2019, this loan was in maturity default. No impairment was recorded as the Company believes that the fair value of the property exceeded the carrying amount of the loans. In April 2019, the Company accepted an assignment of the equity interests in the property in lieu of repayment, and marked the assets received and liabilities assumed to fair value. (6) This loan was extended in April 2019. (7) This loan was modified in April 2019. (8) This loan was repaid in 2019. Preferred Equity Investments As of March 31, 2019 and December 31, 2018 , we held the following preferred equity investments with an aggregate weighted average current yield of 8.74% at March 31, 2019 (dollars in thousands): Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Mandatory Redemption (2) Preferred Equity $ — $ 272,000 $ 143,009 $ 143,183 April 2021 Preferred Equity — 1,762,761 94,612 143,274 June 2022 Total $ — $ 2,034,761 $ 237,621 $ 286,457 (1) Carrying value is net of deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options.

Investments in Unconsolidated J

Investments in Unconsolidated Joint Ventures	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Joint Ventures	Investments in Unconsolidated Joint Ventures We have investments in several real estate joint ventures with various partners. As of March 31, 2019 , the book value of these investments was $3.1 billion , net of investments with negative book values totaling $79.7 million for which we have an implicit commitment to fund future capital needs. As of March 31, 2019 and December 31, 2018 , 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 $ 869.5 million and $808.3 million as of March 31, 2019 and December 31, 2018 , 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, 2019 : Property Partner Ownership (1) Economic (1) Unaudited Approximate Square Feet Acquisition Date (2) Acquisition (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 11 West 34th Street Private Investor/ 30.00% 30.00% 17,150 December 2010 10,800 280 Park Avenue Vornado Realty Trust 50.00% 50.00% 1,219,158 March 2011 400,000 1552-1560 Broadway (4) Jeff Sutton 50.00% 50.00% 57,718 August 2011 136,550 10 East 53rd Street Canadian Pension Plan Investment Board 55.00% 55.00% 354,300 February 2012 252,500 521 Fifth Avenue (5) Plaza Global 50.50% 50.50% 460,000 November 2012 315,000 21 East 66th Street (6) Private Investors 32.28% 32.28% 13,069 December 2012 75,000 650 Fifth Avenue (7) 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 55 West 46th Street Prudential Real Estate Investors 25.00% 25.00% 347,000 November 2014 295,000 Stonehenge Portfolio (8) Various Various Various 1,439,016 February 2015 36,668 605 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 East 57th Street (9) BlackRock, Inc and Stonehenge Partners 51.00% 41.00% 290,482 October 2016 170,000 One Vanderbilt (10) National Pension Service of Korea/Hines Interest LP 71.01% 71.01% — January 2017 3,310,000 Worldwide Plaza RXR Realty / New York REIT / Private Investor 24.35% 24.35% 2,048,725 October 2017 1,725,000 1515 Broadway Allianz Real Estate of America 56.87% 56.87% 1,750,000 November 2017 1,950,000 2 Herald Square Israeli Institutional Investor 51.00% 51.00% 369,000 November 2018 266,000 (1) Ownership interest and economic interest represent the Company's interests in the joint venture as of March 31, 2019 . 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 asset value of the property or properties 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. We recorded our 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 joint venture. (4) The acquisition 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. (5) In March 2019, we, along with our joint venture partner, entered into an agreement to sell this property. (6) 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. (7) 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. (8) In February 2019, we, together with our joint venture partner, closed on the sale of one property from the Stonehenge Portfolio. This sale is further described under Sale of Joint Venture Interest of Properties below. In May 2019, we closed on the sale of our interest in one additional property from the Stonehenge Portfolio. (9) In October 2016, we sold a 49% interest in this property to an investment account managed by BlackRock, Inc. Our 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. Our joint venture with Stonehenge remains consolidated resulting in the combined 51% interest being shown within investments in unconsolidated joint ventures on our balance sheet. (10) The partners' ownership interest in the joint venture is based on their capital contributions, up to an aggregate maximum of 29.0% . As of March 31, 2019 the total of the two partners' ownership interests based on equity contributed was 28.17% . 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, 2019 and December 31, 2018 , the carrying value for acquisition, development and construction arrangements were as follows (dollars in thousands): Loan Type March 31, 2019 December 31, 2018 Maturity Date Mezzanine Loan (1) 44,824 44,357 February 2022 $ 44,824 $ 44,357 (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. In May 2019, the Company purchased a majority and controlling interest in the underlying property. Disposition of Joint Venture Interests or Properties The following table summarizes the investments in unconsolidated joint ventures sold during the three months ended March 31, 2019 : Property Ownership Interest Disposition Date Gross Asset Valuation (in thousands) (1) Gain on Sale (in thousands) (2) 131-137 Spring Street 20.00% January 2019 $ 216,000 $ 17,660 103 East 86th Street (3) 1.00% February 2019 90,500 19 (1) Represents implied gross valuation for the joint venture or sales price of the property. (2) Represents our share of the gain. Gain amounts do not include adjustments for expenses recorded in subsequent periods. (3) Property was part of the Stonehenge Portfolio. Joint Venture Mortgages and Other Loans Payable We generally finance our joint ventures with non-recourse debt. In certain cases we may provide 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, 2019 and December 31, 2018 , respectively, are as follows (dollars in thousands): Property Economic (1) Maturity Date Interest Rate (2) March 31, 2019 December 31, 2018 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 % 500,000 500,000 1515 Broadway 56.87 % March 2025 3.93 % 851,492 855,876 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 % 99,311 99,828 Worldwide Plaza 24.35 % November 2027 3.98 % 1,200,000 1,200,000 Stonehenge Portfolio (5) (6) Various Various 4.20 % 320,047 321,076 Property Economic (1) Maturity Date Interest Rate (2) March 31, 2019 December 31, 2018 Total fixed rate debt $ 5,660,178 $ 5,666,108 Floating Rate Debt: 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 10 East 53rd Street 55.00 % February 2020 L+ 2.25 % 170,000 170,000 1552 Broadway 50.00 % October 2020 L+ 2.65 % 195,000 195,000 55 West 46th Street (7) 25.00 % November 2020 L+ 2.13 % 188,939 185,569 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 % 359,705 360,000 One Vanderbilt (8) 71.01 % September 2021 L+ 2.75 % 375,000 375,000 2 Herald Square (9) 51.00 % November 2021 L+ 1.55 % 133,565 133,565 605 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 % 1,552 1,571 131-137 Spring Street (10) — 141,000 103 East 86th Street (11) — 38,000 Total floating rate debt $ 3,211,761 $ 3,387,705 Total joint venture mortgages and other loans payable $ 8,871,939 $ 9,053,813 Deferred financing costs, net (111,606 ) (103,191 ) Total joint venture mortgages and other loans payable, net $ 8,760,333 $ 8,950,622 (1) Economic interest represents the Company's interests in the joint venture as of March 31, 2019 . 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, 2019 , 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 $133.6 million , $53.8 million , and $132.6 million in fixed-rate mortgages that mature in August 2019, June 2024, and April 2028, respectively. (6) In May 2019, we closed on the sale of our interest in one property from the Stonehenge Portfolio. (7) This loan has a committed amount of $195.0 million , of which $6.1 million was unfunded as of March 31, 2019 . (8) This loan is a $1.75 billion construction facility, with reductions in interest cost 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. (9) This loan has a committed amount of $150.0 million . (10) In January 2019, we closed on the sale of our interest in the property. (11) In February 2019, we, along with our joint venture partner, closed on the sale of the property. We act as the operating partner and day-to-day manager for all our joint ventures, except for Worldwide Plaza, 800 Third Avenue, 280 Park Avenue, 21 East 66th 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 $2.5 million from these services, net of our ownership share of the joint ventures, for the three months ended March 31, 2019 . We earned $3.8 million from these services, net of our ownership share of the joint ventures, for the three months ended March 31, 2018 . 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, 2019 and December 31, 2018 are as follows (in thousands): March 31, 2019 December 31, 2018 Assets (1) Commercial real estate property, net $ 14,362,952 $ 14,347,673 Cash and restricted cash 370,832 381,301 Tenant and other receivables, related party receivables, and deferred rents receivable 321,696 273,141 Debt and preferred equity investments, net 44,824 44,357 Other assets 2,191,441 2,187,166 Total assets $ 17,291,745 $ 17,233,638 Liabilities and equity (1) Mortgages and other loans payable, net $ 8,760,333 $ 8,950,622 Deferred revenue/gain 1,620,437 1,660,838 Lease liabilities 901,808 637,168 Other liabilities 341,134 309,145 Equity 5,668,033 5,675,865 Total liabilities and equity $ 17,291,745 $ 17,233,638 Company's investments in unconsolidated joint ventures $ 3,055,368 $ 3,019,020 (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, from acquisition date through the three months ended March 31, 2019 and 2018 , are as follows (in thousands): Three Months Ended March 31, 2019 2018 Total revenues $ 307,519 $ 320,941 Operating expenses 54,124 59,773 Operating lease rent 5,901 4,393 Real estate taxes 54,236 57,027 Interest expense, net of interest income 96,623 89,741 Amortization of deferred financing costs 5,216 5,116 Depreciation and amortization 104,331 105,080 Total expenses 320,431 321,130 Net loss before gain on sale (1) $ (12,912 ) $ (189 ) Company's equity in net (loss) income from unconsolidated joint ventures (1) $ (5,234 ) $ 4,036 (1) The combined statements of operations and the Company's equity in net (loss) 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

Deferred Costs	3 Months Ended
	Mar. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs	Deferred Costs Deferred costs at March 31, 2019 and December 31, 2018 consisted of the following (in thousands): March 31, 2019 December 31, 2018 Deferred leasing costs $ 463,521 $ 453,833 Less: accumulated amortization (251,906 ) (244,723 ) Deferred costs, net $ 211,615 $ 209,110

Mortgages and Other Loans Payab

Mortgages and Other Loans Payable	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 , respectively, were as follows (dollars in thousands): Property Maturity Date Interest Rate (1) March 31, 2019 December 31, 2018 Fixed Rate Debt: 762 Madison Avenue February 2022 5.00 % 771 771 100 Church Street July 2022 4.68 % 212,463 213,208 420 Lexington Avenue October 2024 3.99 % 300,000 300,000 400 East 58th Street (2) November 2026 3.00 % 39,724 39,931 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 % 35,634 35,807 315 West 33rd Street February 2027 4.17 % 250,000 250,000 Total fixed rate debt $ 1,388,592 $ 1,389,717 Floating Rate Debt: FHLB Facility May 2019 L+ 0.27 % 13,000 13,000 2017 Master Repurchase Agreement June 2019 L+ 2.34 % 300,000 300,000 FHLB Facility December 2019 L+ 0.18 % 14,500 14,500 FHLB Facility January 2020 L+ 0.26 % 10,000 — 133 Greene Street August 2020 L+ 2.00 % 15,523 15,523 609 Fifth Avenue March 2021 L+ 2.40 % 49,872 — 185 Broadway (4) November 2021 L+ 2.85 % 111,869 111,869 712 Madison Avenue December 2021 L+ 2.50 % 28,000 28,000 115 Spring Street September 2023 L+ 3.40 % 65,550 65,550 719 Seventh Avenue September 2023 L+ 1.20 % 50,000 50,000 Total floating rate debt $ 658,314 $ 598,442 Total mortgages and other loans payable $ 2,046,906 $ 1,988,159 Deferred financing costs, net of amortization (28,345 ) (26,919 ) Total mortgages and other loans payable, net $ 2,018,561 $ 1,961,240 (1) Interest rate as of March 31, 2019 , 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) This loan is a $225.0 million construction facility, with reductions in interest cost based on meeting certain conditions, and has an initial three -year term with two one -year extension options. Advances under the loan are subject to incurred costs and funded equity requirements. At March 31, 2019 and December 31, 2018 , the gross book value of the properties and debt and preferred equity investments collateralizing the mortgages and other loans payable was approximately $4.1 billion and $3.9 billion , respectively. Federal Home Loan Bank of New York Facility The Company's wholly-owned subsidiary, Ticonderoga Insurance Company, or Ticonderoga, a Vermont licensed captive insurance company, is a member of the Federal Home Loan Bank of New York, or FHLBNY. As a member, Ticonderoga may borrow funds from the FHLBNY in the form of secured advances. As of March 31, 2019 , we had $13.0 million , $14.5 million and $10.0 million in outstanding secured advances with a borrowing rate of 30 -day LIBOR plus 27 basis points, 30 -day LIBOR plus 18 basis points and 30 -day LIBOR plus 26 basis points, respectively. Master Repurchase Agreement The Company entered into a Master Repurchase Agreement, or MRA, known as the 2017 MRA, which provides 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 facility 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. The 2017 MRA has 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. In June 2018, we exercised a one year extension option. At March 31, 2019 , the facility had a carrying value of $299.9 million , net of deferred financing costs. 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, 2019 , 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, 2019 , 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, 2019 , 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, 2019 , the facility fee was 20 basis points. As of March 31, 2019 , we had $11.8 million of outstanding letters of credit, $790.0 million drawn under the revolving credit facility and $1.5 billion outstanding under the term loan facilities, with total undrawn capacity of $0.7 billion under the 2017 credit facility. At March 31, 2019 and December 31, 2018 , the revolving credit facility had a carrying value of $782.7 million and $492.2 million , respectively, net of deferred financing costs. At March 31, 2019 and December 31, 2018 , 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. 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, 2019 and December 31, 2018 , respectively, by scheduled maturity date (amounts in thousands): Issuance March 31, March 31, December 31, Interest Rate (1) Initial Term (in Years) Maturity Date March 16, 2010 (2) $ 250,000 $ 250,000 $ 250,000 7.75 % 10 March 2020 August 7, 2018 (3) (4) 350,000 350,000 350,000 L+ 0.98 % 3 August 2021 October 5, 2017 (3) 500,000 499,616 499,591 3.25 % 5 October 2022 November 15, 2012 (5) 300,000 303,918 304,168 4.50 % 10 December 2022 December 17, 2015 (2) 100,000 100,000 100,000 4.27 % 10 December 2025 $ 1,500,000 $ 1,503,534 $ 1,503,759 Deferred financing costs, net (8,044 ) (8,545 ) $ 1,500,000 $ 1,495,490 $ 1,495,214 (1) Interest rate as of March 31, 2019 , taking into account interest rate hedges in effect during the period. Floating rate notes are presented with the stated spread over 3-month LIBOR, unless otherwise specified. 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 and the Operating Partnership as co-obligors. (3) Issued by the Operating Partnership with the Company as the guarantor. (4) Beginning on August 8, 2019 and at any time thereafter, the notes are subject to redemption at the Company's option, in whole but not in part, at a redemption price equal to 100% of the principal amount of the notes, plus unpaid accrued interest thereon to the redemption date. (5) In October 2017, the Company and the Operating Partnership 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, 2019 and December 31, 2018 , 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, 2019 , including as-of-right extension options and put options, were as follows (in thousands): Scheduled Amortization Mortgages and Other Loans Payable Revolving Credit Facility Unsecured Term Loans Trust Preferred Securities Senior Unsecured Notes Total Joint Venture Debt Remaining 2019 $ 5,143 $ 27,500 $ — $ — $ — $ — $ 32,643 $ 112,359 2020 11,118 325,523 — — — 250,000 586,641 251,433 2021 11,638 189,741 — — — 350,000 551,379 522,359 2022 9,430 198,555 — — — 800,000 1,007,985 220,810 2023 7,301 115,550 790,000 1,300,000 — — 2,212,851 277,996 Thereafter 9,291 1,136,116 — 200,000 100,000 100,000 1,545,407 2,430,198 $ 53,921 $ 1,992,985 $ 790,000 $ 1,500,000 $ 100,000 $ 1,500,000 $ 5,936,906 $ 3,815,155 Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands): Three Months Ended March 31, 2019 2018 Interest expense before capitalized interest $ 60,810 $ 54,132 Interest on financing leases 804 786 Interest capitalized (10,509 ) (6,686 ) Interest income (580 ) (316 ) Interest expense, net $ 50,525 $ 47,916

Corporate Indebtedness

Corporate Indebtedness	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Corporate Indebtedness	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, 2019 and December 31, 2018 , respectively, were as follows (dollars in thousands): Property Maturity Date Interest Rate (1) March 31, 2019 December 31, 2018 Fixed Rate Debt: 762 Madison Avenue February 2022 5.00 % 771 771 100 Church Street July 2022 4.68 % 212,463 213,208 420 Lexington Avenue October 2024 3.99 % 300,000 300,000 400 East 58th Street (2) November 2026 3.00 % 39,724 39,931 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 % 35,634 35,807 315 West 33rd Street February 2027 4.17 % 250,000 250,000 Total fixed rate debt $ 1,388,592 $ 1,389,717 Floating Rate Debt: FHLB Facility May 2019 L+ 0.27 % 13,000 13,000 2017 Master Repurchase Agreement June 2019 L+ 2.34 % 300,000 300,000 FHLB Facility December 2019 L+ 0.18 % 14,500 14,500 FHLB Facility January 2020 L+ 0.26 % 10,000 — 133 Greene Street August 2020 L+ 2.00 % 15,523 15,523 609 Fifth Avenue March 2021 L+ 2.40 % 49,872 — 185 Broadway (4) November 2021 L+ 2.85 % 111,869 111,869 712 Madison Avenue December 2021 L+ 2.50 % 28,000 28,000 115 Spring Street September 2023 L+ 3.40 % 65,550 65,550 719 Seventh Avenue September 2023 L+ 1.20 % 50,000 50,000 Total floating rate debt $ 658,314 $ 598,442 Total mortgages and other loans payable $ 2,046,906 $ 1,988,159 Deferred financing costs, net of amortization (28,345 ) (26,919 ) Total mortgages and other loans payable, net $ 2,018,561 $ 1,961,240 (1) Interest rate as of March 31, 2019 , 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) This loan is a $225.0 million construction facility, with reductions in interest cost based on meeting certain conditions, and has an initial three -year term with two one -year extension options. Advances under the loan are subject to incurred costs and funded equity requirements. At March 31, 2019 and December 31, 2018 , the gross book value of the properties and debt and preferred equity investments collateralizing the mortgages and other loans payable was approximately $4.1 billion and $3.9 billion , respectively. Federal Home Loan Bank of New York Facility The Company's wholly-owned subsidiary, Ticonderoga Insurance Company, or Ticonderoga, a Vermont licensed captive insurance company, is a member of the Federal Home Loan Bank of New York, or FHLBNY. As a member, Ticonderoga may borrow funds from the FHLBNY in the form of secured advances. As of March 31, 2019 , we had $13.0 million , $14.5 million and $10.0 million in outstanding secured advances with a borrowing rate of 30 -day LIBOR plus 27 basis points, 30 -day LIBOR plus 18 basis points and 30 -day LIBOR plus 26 basis points, respectively. Master Repurchase Agreement The Company entered into a Master Repurchase Agreement, or MRA, known as the 2017 MRA, which provides 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 facility 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. The 2017 MRA has 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. In June 2018, we exercised a one year extension option. At March 31, 2019 , the facility had a carrying value of $299.9 million , net of deferred financing costs. 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, 2019 , 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, 2019 , 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, 2019 , 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, 2019 , the facility fee was 20 basis points. As of March 31, 2019 , we had $11.8 million of outstanding letters of credit, $790.0 million drawn under the revolving credit facility and $1.5 billion outstanding under the term loan facilities, with total undrawn capacity of $0.7 billion under the 2017 credit facility. At March 31, 2019 and December 31, 2018 , the revolving credit facility had a carrying value of $782.7 million and $492.2 million , respectively, net of deferred financing costs. At March 31, 2019 and December 31, 2018 , 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. 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, 2019 and December 31, 2018 , respectively, by scheduled maturity date (amounts in thousands): Issuance March 31, March 31, December 31, Interest Rate (1) Initial Term (in Years) Maturity Date March 16, 2010 (2) $ 250,000 $ 250,000 $ 250,000 7.75 % 10 March 2020 August 7, 2018 (3) (4) 350,000 350,000 350,000 L+ 0.98 % 3 August 2021 October 5, 2017 (3) 500,000 499,616 499,591 3.25 % 5 October 2022 November 15, 2012 (5) 300,000 303,918 304,168 4.50 % 10 December 2022 December 17, 2015 (2) 100,000 100,000 100,000 4.27 % 10 December 2025 $ 1,500,000 $ 1,503,534 $ 1,503,759 Deferred financing costs, net (8,044 ) (8,545 ) $ 1,500,000 $ 1,495,490 $ 1,495,214 (1) Interest rate as of March 31, 2019 , taking into account interest rate hedges in effect during the period. Floating rate notes are presented with the stated spread over 3-month LIBOR, unless otherwise specified. 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 and the Operating Partnership as co-obligors. (3) Issued by the Operating Partnership with the Company as the guarantor. (4) Beginning on August 8, 2019 and at any time thereafter, the notes are subject to redemption at the Company's option, in whole but not in part, at a redemption price equal to 100% of the principal amount of the notes, plus unpaid accrued interest thereon to the redemption date. (5) In October 2017, the Company and the Operating Partnership 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, 2019 and December 31, 2018 , 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, 2019 , including as-of-right extension options and put options, were as follows (in thousands): Scheduled Amortization Mortgages and Other Loans Payable Revolving Credit Facility Unsecured Term Loans Trust Preferred Securities Senior Unsecured Notes Total Joint Venture Debt Remaining 2019 $ 5,143 $ 27,500 $ — $ — $ — $ — $ 32,643 $ 112,359 2020 11,118 325,523 — — — 250,000 586,641 251,433 2021 11,638 189,741 — — — 350,000 551,379 522,359 2022 9,430 198,555 — — — 800,000 1,007,985 220,810 2023 7,301 115,550 790,000 1,300,000 — — 2,212,851 277,996 Thereafter 9,291 1,136,116 — 200,000 100,000 100,000 1,545,407 2,430,198 $ 53,921 $ 1,992,985 $ 790,000 $ 1,500,000 $ 100,000 $ 1,500,000 $ 5,936,906 $ 3,815,155 Consolidated interest expense, excluding capitalized interest, was comprised of the following (in thousands): Three Months Ended March 31, 2019 2018 Interest expense before capitalized interest $ 60,810 $ 54,132 Interest on financing leases 804 786 Interest capitalized (10,509 ) (6,686 ) Interest income (580 ) (316 ) Interest expense, net $ 50,525 $ 47,916

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	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, who serves as a member and as the chairman emeritus 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 $0.9 million and $1.0 million for the three months ended March 31, 2019 and 2018 , respectively. We also recorded expenses, inclusive of capitalized expenses, of $2.9 million and $4.0 million for the three months ended March 31, 2019 and 2018 , 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, 2019 and 2018 , respectively. One Vanderbilt Investment In December 2016, we entered into agreements with entities owned and controlled by our Chairman and CEO, Marc Holliday, and our President, 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, 2019 and December 31, 2018 consisted of the following (in thousands): March 31, 2019 December 31, 2018 Due from joint ventures $ 20,723 $ 18,655 Other 8,735 9,378 Related party receivables $ 29,458 $ 28,033

Noncontrolling Interests on the

Noncontrolling Interests on the Company's Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interests on the Company's Consolidated Financial Statements	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, 2019 and December 31, 2018 , the noncontrolling interest unit holders owned 4.87% , or 4,260,685 units, and 4.70% , or 4,130,579 units, of the Operating Partnership, respectively. As of March 31, 2019 , 4,260,685 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 a summary of the activity relating to the noncontrolling interests in the Operating Partnership for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of period $ 387,805 $ 461,954 Distributions (3,643 ) (15,000 ) Issuance of common units 14,135 23,655 Redemption of common units (16,143 ) (60,718 ) Net income 2,278 12,216 Accumulated other comprehensive income allocation (1,003 ) (66 ) Fair value adjustment 28,932 (34,236 ) Balance at end of period $ 412,361 $ 387,805 Preferred Units of Limited Partnership Interest in the Operating Partnership Below is a summary of the preferred units of limited partnership interest in the Operating Partnership as of March 31, 2019 : Issuance Number of Units Authorized Number of Units Issued Dividends Per Unit (1) Liquidation Preference Per Unit (2) Conversion Price Per Unit (3) Date of Issuance 4.50% Series G (4) 1,902,000 1,902,000 $ 1.1250 $ 25.00 $ 88.50 January 2012 7.00% Series F 60 60 $ 70.0000 $ 1,000.00 $ 29.12 January 2007 3.50% Series K 700,000 563,954 $ 0.8750 $ 25.00 $ 134.67 August 2014 4.00% Series L 500,000 378,634 $ 1.0000 $ 25.00 — August 2014 3.75% Series M 1,600,000 1,600,000 $ 0.9375 $ 25.00 — February 2015 3.00% Series N (5) 552,303 552,303 $ 0.7500 $ 25.00 — June 2015 Series O (6) 1 1 (6 ) (6 ) — June 2015 4.00% Series P 200,000 200,000 $ 1.0000 $ 25.00 — July 2015 3.50% Series Q 268,000 268,000 $ 0.8750 $ 25.00 $ 148.95 July 2015 3.50% Series R 400,000 400,000 $ 0.8750 $ 25.00 $ 154.89 August 2015 4.00% Series S 1,077,280 1,077,280 $ 1.0000 $ 25.00 — August 2015 2.75% Series T 230,000 230,000 $ 0.6875 $ 25.00 $ 119.02 March 2016 4.50% Series U (7) 680,000 680,000 $ 1.1250 $ 25.00 — March 2016 3.50% Series A (8) 109,161 109,161 $ 35.0000 $ 1,000.00 — August 2015 (1) Dividends are cumulative, subject to certain provisions. (2) Units are redeemable at any time at par for cash at the option of the unitholder unless otherwise specified. (3) If applicable, 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) the amount shown in the table. (4) Common units of limited partnership interest in the Operating Partnership issued in a conversion 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. (5) All of the outstanding units were redeemed at par for cash by the unitholder during the three months ended March 31, 2019 . (6) The holder of the Series O preferred unit is entitled to quarterly dividends in an amount calculated as (i) 1,350 multiplied by (ii) the current distribution per common unit of limited partnership in SL Green Operating Partnership. The holder has the right to require the Operating Partnership to repurchase the Series O unit for cash at a price that is determined based on the closing price of the Company's common stock at the time such right is exercised. The unit's liquidation preference is the fair market value of the unit at the time of a liquidation event. (7) The annual dividend is subject to reduction upon the occurrence of certain circumstances. The minimum annual dividend is $0.75 per unit. (8) Issued through a consolidated subsidiary. The units 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, 2019 , no Subsidiary Series B Preferred Units have been issued. Below is a summary of the activity relating to the preferred units in the Operating Partnership for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of period $ 300,427 $ 301,735 Issuance of preferred units — — Redemption of preferred units (15,142 ) (1,308 ) Balance at end of period $ 285,285 $ 300,427

Stockholders' Equity of the Com

Stockholders' Equity of the Company	3 Months Ended
	Mar. 31, 2019
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, 2019 , 83,272,202 shares of common stock and no shares of excess stock were issued and outstanding. Share Repurchase Program In August 2016, our Board of Directors approved a share repurchase plan under which we can buy up to $1.0 billion of shares of our common stock. The Board of Directors has since authorized three separate $500.0 million increases to the size of the share repurchase program in the fourth quarter of 2017, second quarter of 2018, and fourth quarter of 2018, bringing the total program size to $2.5 billion . At March 31, 2019 , repurchases executed 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 Year ended 2017 8,342,411 $101.64 8,342,411 Year ended 2018 9,744,911 $96.22 18,087,322 First quarter 2019 397,783 $86.07 18,485,105 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. The following table summarizes SL Green common stock issued, and proceeds received from dividend reinvestments and/or stock purchases under the DRSPP for the three months ended March 31, 2019 and 2018 , respectively (dollars in thousands): Three Months Ended March 31, 2019 2018 Shares of common stock issued 540 447 Dividend reinvestments/stock purchases under the DRSPP $ 47 $ 42 Earnings per Share We use the two-class method of computing earnings per share (“EPS”), which is an earnings allocation formula that determines EPS for common stock and any participating securities according to dividends declared (whether paid or unpaid). Under the two-class method, basic EPS is computed by dividing the income available to common stockholders by the weighted-average number of common stock shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur from share equivalent activity. SL Green's earnings per share for the three months ended March 31, 2019 and 2018 are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SL Green common stockholders $ 43,792 $ 101,766 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net income attributable to SL Green common stockholders (numerator for basic earnings per share) $ 43,668 $ 101,615 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Add back: Effect of dilutive securities (redemption of units to common shares) 2,278 5,272 Income attributable to SL Green common stockholders (numerator for diluted earnings per share) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic Shares: Weighted average common stock outstanding 83,313 90,520 Effect of Dilutive Securities: Operating Partnership units redeemable for common shares 4,333 4,683 Stock-based compensation plans 164 53 Diluted weighted average common stock outstanding 87,810 95,256 SL Green has excluded 1,211,943 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2019 as they were anti-dilutive. SL Green has excluded 1,210,802 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2018 as they were anti-dilutive. Accumulated Other Comprehensive (Loss) Income The following tables set forth the changes in accumulated other comprehensive (loss) income by component as of March 31, 2019 (in thousands): Net unrealized gain (loss) on derivative instruments ( 1 ) SL Green’s share of joint venture net unrealized gain (loss) on derivative instruments ( 2 ) Net unrealized gain on marketable securities Total Balance at December 31, 2018 $ 9,716 $ 4,299 $ 1,093 $ 15,108 Other comprehensive (loss) income before reclassifications (11,864 ) (6,972 ) 731 (18,105 ) Amounts reclassified from accumulated other comprehensive income (530 ) (478 ) — (1,008 ) Balance at March 31, 2019 $ (2,678 ) $ (3,151 ) $ 1,824 $ (4,005 ) (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, 2019 and December 31, 2018 , 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 $0.8 million and $1.3 million , respectively. (2) Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net (loss) income from unconsolidated joint ventures in the respective consolidated statements of operations.

Partners' Capital of the Operat

Partners' Capital of the Operating Partnership	3 Months Ended
	Mar. 31, 2019
Stockholders' Equity
Partners' Capital of the Operating Partnership	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, 2019 , 83,272,202 shares of common stock and no shares of excess stock were issued and outstanding. Share Repurchase Program In August 2016, our Board of Directors approved a share repurchase plan under which we can buy up to $1.0 billion of shares of our common stock. The Board of Directors has since authorized three separate $500.0 million increases to the size of the share repurchase program in the fourth quarter of 2017, second quarter of 2018, and fourth quarter of 2018, bringing the total program size to $2.5 billion . At March 31, 2019 , repurchases executed 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 Year ended 2017 8,342,411 $101.64 8,342,411 Year ended 2018 9,744,911 $96.22 18,087,322 First quarter 2019 397,783 $86.07 18,485,105 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. The following table summarizes SL Green common stock issued, and proceeds received from dividend reinvestments and/or stock purchases under the DRSPP for the three months ended March 31, 2019 and 2018 , respectively (dollars in thousands): Three Months Ended March 31, 2019 2018 Shares of common stock issued 540 447 Dividend reinvestments/stock purchases under the DRSPP $ 47 $ 42 Earnings per Share We use the two-class method of computing earnings per share (“EPS”), which is an earnings allocation formula that determines EPS for common stock and any participating securities according to dividends declared (whether paid or unpaid). Under the two-class method, basic EPS is computed by dividing the income available to common stockholders by the weighted-average number of common stock shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur from share equivalent activity. SL Green's earnings per share for the three months ended March 31, 2019 and 2018 are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SL Green common stockholders $ 43,792 $ 101,766 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net income attributable to SL Green common stockholders (numerator for basic earnings per share) $ 43,668 $ 101,615 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Add back: Effect of dilutive securities (redemption of units to common shares) 2,278 5,272 Income attributable to SL Green common stockholders (numerator for diluted earnings per share) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic Shares: Weighted average common stock outstanding 83,313 90,520 Effect of Dilutive Securities: Operating Partnership units redeemable for common shares 4,333 4,683 Stock-based compensation plans 164 53 Diluted weighted average common stock outstanding 87,810 95,256 SL Green has excluded 1,211,943 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2019 as they were anti-dilutive. SL Green has excluded 1,210,802 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2018 as they were anti-dilutive. Accumulated Other Comprehensive (Loss) Income The following tables set forth the changes in accumulated other comprehensive (loss) income by component as of March 31, 2019 (in thousands): Net unrealized gain (loss) on derivative instruments ( 1 ) SL Green’s share of joint venture net unrealized gain (loss) on derivative instruments ( 2 ) Net unrealized gain on marketable securities Total Balance at December 31, 2018 $ 9,716 $ 4,299 $ 1,093 $ 15,108 Other comprehensive (loss) income before reclassifications (11,864 ) (6,972 ) 731 (18,105 ) Amounts reclassified from accumulated other comprehensive income (530 ) (478 ) — (1,008 ) Balance at March 31, 2019 $ (2,678 ) $ (3,151 ) $ 1,824 $ (4,005 ) (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, 2019 and December 31, 2018 , 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 $0.8 million and $1.3 million , respectively. (2) Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net (loss) income from unconsolidated joint ventures in the respective consolidated statements of operations.
SL Green Operating Partnership
Stockholders' Equity
Partners' Capital of the Operating Partnership	Partners' Capital of the Operating Partnership The Company is the sole managing general partner of the Operating Partnership and at March 31, 2019 owned 83,272,202 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, 2019 , limited partners other than SL Green owned 4.87% , or 4,260,685 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, 2019 and 2018 , respectively, are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SLGOP common unitholders $ 46,070 $ 107,038 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net Income attributable to SLGOP common unitholders (numerator for basic earnings per unit) $ 45,946 $ 106,887 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Income attributable to SLGOP common unitholders (numerator for diluted earnings per unit) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic units: Weighted average common units outstanding 87,646 95,203 Effect of Dilutive Securities: Stock-based compensation plans 164 53 Diluted weighted average common units outstanding 87,810 95,256 The Operating Partnership has excluded 1,211,943 common unit equivalents from the diluted units outstanding for the three months ended March 31, 2019 as they were anti-dilutive. The Operating Partnership has excluded 1,210,802 common unit equivalents from the diluted units outstanding for the three months ended March 31, 2018 as they were anti-dilutive.

Share-based Compensation

Share-based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation	Share-based Compensation We have share-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. 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, 2019 , 4.5 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. Stock Options and Class O LTIP Units Options are granted 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, 2019 and the year ended December 31, 2018 . There were no grants during the three months ended March 31, 2019 . March 31, 2019 December 31, 2018 Dividend yield none 2.85 % Expected life zero 3.5 years Risk-free interest rate none 2.48 % Expected stock price volatility none 22.00 % A summary of the status of the Company's stock options as of March 31, 2019 and December 31, 2018 , and changes during the three months ended March 31, 2019 and year ended December 31, 2018 are as follows: March 31, 2019 December 31, 2018 Options Outstanding Weighted Average Exercise Price Options Outstanding Weighted Average Exercise Price Balance at beginning of period 1,137,017 $ 103.54 1,548,719 $ 101.48 Granted — — 6,000 97.91 Exercised — — (316,302 ) 90.22 Lapsed or canceled (5,999 ) 110.56 (101,400 ) 113.22 Balance at end of period 1,131,018 $ 103.50 1,137,017 $ 103.54 Options exercisable at end of period 994,045 $ 103.00 783,035 $ 101.28 Total fair value of options granted during the period $ — $ 84,068 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 3.2 years and the remaining average contractual life of the options exercisable was 3.2 years. During the three months ended March 31, 2019 , we recognized compensation expense for these options of $0.6 million . During the three months ended March 31, 2018 , we recognized compensation expense for these options of $1.6 million . As of March 31, 2019 , there was $1.9 million of total unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted average period of 0.8 years. Restricted Shares Shares are 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, 2019 and December 31, 2018 and charges during the three months ended March 31, 2019 and the year ended December 31, 2018 , are as follows: March 31, 2019 December 31, 2018 Balance at beginning of period 3,452,016 3,298,216 Granted 6,000 162,900 Canceled (5,950 ) (9,100 ) Balance at end of period 3,452,066 3,452,016 Vested during the period 110,274 92,114 Compensation expense recorded $ 3,411,841 $ 12,757,704 Total fair value of restricted stock granted during the period $ 474,480 $ 13,440,503 The fair value of restricted stock that vested during the three months ended March 31, 2019 and the year ended December 31, 2018 was $11.8 million and $9.8 million , respectively. As of March 31, 2019 there was $19.4 million of total unrecognized compensation cost related to restricted stock, which is expected to be recognized over a weighted average period of 2.1 years . We granted LTIP Units, which include bonus, time-based and performance-based awards, with a fair value of $41.6 million and $22.0 million as of March 31, 2019 and December 31, 2018 , 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, 2019 , there was $28.5 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 2.7 years . During the three months ended March 31, 2019 , we recorded compensation expense related to bonus, time-based and performance based awards of $8.0 million . During the three months ended March 31, 2018 we recorded compensation expense related to bonus, time-based and performance based awards of $6.9 million . For the three months ended March 31, 2019 , $0.5 million was capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options. For the three months ended March 31, 2018 , $1.6 million was capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options. 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, 2019 , 14,298 phantom stock units and 9,722 shares of common stock were issued to our board of directors. We recorded compensation expense of $1.9 million during the three months ended March 31, 2019 related to the Deferred Compensation Plan. We recorded compensation expense of $2.2 million during the three months ended March 31, 2018 related to the Deferred Compensation Plan. As of March 31, 2019 , there were 124,576 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 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, 2019 , 120,085 shares of our common stock had been issued under the ESPP.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Accumulated Other Comprehensive Income	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, 2019 , 83,272,202 shares of common stock and no shares of excess stock were issued and outstanding. Share Repurchase Program In August 2016, our Board of Directors approved a share repurchase plan under which we can buy up to $1.0 billion of shares of our common stock. The Board of Directors has since authorized three separate $500.0 million increases to the size of the share repurchase program in the fourth quarter of 2017, second quarter of 2018, and fourth quarter of 2018, bringing the total program size to $2.5 billion . At March 31, 2019 , repurchases executed 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 Year ended 2017 8,342,411 $101.64 8,342,411 Year ended 2018 9,744,911 $96.22 18,087,322 First quarter 2019 397,783 $86.07 18,485,105 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. The following table summarizes SL Green common stock issued, and proceeds received from dividend reinvestments and/or stock purchases under the DRSPP for the three months ended March 31, 2019 and 2018 , respectively (dollars in thousands): Three Months Ended March 31, 2019 2018 Shares of common stock issued 540 447 Dividend reinvestments/stock purchases under the DRSPP $ 47 $ 42 Earnings per Share We use the two-class method of computing earnings per share (“EPS”), which is an earnings allocation formula that determines EPS for common stock and any participating securities according to dividends declared (whether paid or unpaid). Under the two-class method, basic EPS is computed by dividing the income available to common stockholders by the weighted-average number of common stock shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur from share equivalent activity. SL Green's earnings per share for the three months ended March 31, 2019 and 2018 are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SL Green common stockholders $ 43,792 $ 101,766 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net income attributable to SL Green common stockholders (numerator for basic earnings per share) $ 43,668 $ 101,615 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Add back: Effect of dilutive securities (redemption of units to common shares) 2,278 5,272 Income attributable to SL Green common stockholders (numerator for diluted earnings per share) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic Shares: Weighted average common stock outstanding 83,313 90,520 Effect of Dilutive Securities: Operating Partnership units redeemable for common shares 4,333 4,683 Stock-based compensation plans 164 53 Diluted weighted average common stock outstanding 87,810 95,256 SL Green has excluded 1,211,943 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2019 as they were anti-dilutive. SL Green has excluded 1,210,802 common stock equivalents from the diluted shares outstanding for the three months ended March 31, 2018 as they were anti-dilutive. Accumulated Other Comprehensive (Loss) Income The following tables set forth the changes in accumulated other comprehensive (loss) income by component as of March 31, 2019 (in thousands): Net unrealized gain (loss) on derivative instruments ( 1 ) SL Green’s share of joint venture net unrealized gain (loss) on derivative instruments ( 2 ) Net unrealized gain on marketable securities Total Balance at December 31, 2018 $ 9,716 $ 4,299 $ 1,093 $ 15,108 Other comprehensive (loss) income before reclassifications (11,864 ) (6,972 ) 731 (18,105 ) Amounts reclassified from accumulated other comprehensive income (530 ) (478 ) — (1,008 ) Balance at March 31, 2019 $ (2,678 ) $ (3,151 ) $ 1,824 $ (4,005 ) (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, 2019 and December 31, 2018 , 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 $0.8 million and $1.3 million , respectively. (2) Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net (loss) income from unconsolidated joint ventures in the respective consolidated statements of operations.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
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. 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, 2019 and December 31, 2018 (in thousands): March 31, 2019 Total Level 1 Level 2 Level 3 Assets: Marketable securities $ 29,406 $ — $ 29,406 $ — Interest rate cap and swap agreements (included in other assets) $ 13,644 $ — $ 13,644 $ — Liabilities: Interest rate cap and swap agreements (included in other liabilities) $ 15,644 $ — $ 15,644 $ — December 31, 2018 Total Level 1 Level 2 Level 3 Assets: Marketable securities $ 28,638 $ — $ 28,638 $ — Interest rate cap and swap agreements (included in other assets) $ 18,676 $ — $ 18,676 $ — Liabilities: Interest rate cap and swap agreements (included in other liabilities) $ 7,663 $ — $ 7,663 $ — We determine 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. 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, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Debt and preferred equity investments $ 2,272,241 (2) $ 2,099,393 (2) Fixed rate debt $ 3,542,126 $ 3,627,127 $ 3,543,476 $ 3,230,127 Variable rate debt 2,398,314 2,404,641 2,048,442 2,057,966 $ 5,940,440 $ 6,031,768 $ 5,591,918 $ 5,288,093 (1) Amounts exclude net deferred financing costs. (2) At March 31, 2019 , debt and preferred equity investments had an estimated fair value ranging between $2.3 billion and $2.5 billion . At December 31, 2018 , 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, 2019 and December 31, 2018 . 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.

Financial Instruments_ Derivati

Financial Instruments: Derivatives and Hedging	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments: Derivatives and Hedging	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. 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, 2019 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 (dollars in thousands). Notional Value Strike Rate Effective Date Expiration Date Balance Sheet Location Fair Value Interest Rate Cap $ 137,500 4.000 % September 2017 September 2019 Other Assets $ — Interest Rate Cap 111,869 3.500 % November 2018 December 2019 Other Assets — Interest Rate Swap 100,000 1.928 % December 2017 November 2020 Other Assets 574 Interest Rate Swap 100,000 1.934 % December 2017 November 2020 Other Assets 565 Interest Rate Cap 85,000 4.000 % March 2019 March 2021 Other Assets 1 Interest Rate Swap 200,000 1.131 % July 2016 July 2023 Other Assets 8,418 Interest Rate Swap 100,000 1.161 % July 2016 July 2023 Other Assets 4,086 Interest Rate Swap 150,000 2.696 % January 2019 January 2024 Other Liabilities (3,688 ) Interest Rate Swap 150,000 2.721 % January 2019 January 2026 Other Liabilities (5,078 ) Interest Rate Swap 200,000 2.740 % January 2019 January 2026 Other Liabilities (6,878 ) $ (2,000 ) During the three months ended March 31, 2019 , 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. 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. 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, 2019 , 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 $15.7 million . As of March 31, 2019 , 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 $16.2 million at March 31, 2019 . 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 $0.9 million of the current balance held in accumulated other comprehensive income will be reclassified into interest expense and $0.4 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, 2019 and 2018 , respectively (in thousands): Amount of Gain (Loss) Location of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Gain (Loss) Three Months Ended March 31, Three Months Ended March 31, Derivative 2019 2018 2019 2018 Interest Rate Swaps/Caps $ (11,963 ) $ 7,282 Interest expense $ 535 $ (338 ) Share of unconsolidated joint ventures' derivative instruments (5,369 ) 3,313 Equity in net income from unconsolidated joint ventures 368 (90 ) $ (17,332 ) $ 10,595 $ 903 $ (428 )

Rental Income

Rental Income	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Rental Income	Rental Income The Operating Partnership is the lessor and the sublessor to tenants under operating leases with expiration dates ranging from April 1, 2019 to 2064. The minimum rental amounts due under the leases are generally either subject to scheduled fixed increases or adjustments. The leases generally also require that the tenants reimburse us for increases in certain operating costs and real estate taxes above their base year costs. Approximate future minimum rents to be received over the next five years and thereafter for non-cancelable operating leases in effect at March 31, 2019 for the consolidated properties, including consolidated joint venture properties, and our share of unconsolidated joint venture properties, are as follows (in thousands): Consolidated Properties Unconsolidated Properties Remaining 2019 $ 638,682 $ 265,578 2020 801,572 385,998 2021 654,113 392,375 2022 591,562 373,353 2023 527,679 344,592 2024 487,263 315,338 Thereafter 3,068,298 1,854,001 $ 6,769,169 $ 3,931,235 As of December 31, 2018 , under ASC 840, approximate future minimum rents to be received over the next five years and thereafter for non-cancelable operating leases for the consolidated properties, including consolidated joint venture properties, and our share of unconsolidated joint venture properties are as follows (in thousands): Consolidated Properties Unconsolidated Properties 2019 $ 830,336 $ 348,060 2020 765,610 375,228 2021 625,956 380,886 2022 562,250 348,222 2023 500,499 333,501 Thereafter 3,272,014 2,098,995 $ 6,556,665 $ 3,884,892 The components of lease revenues were as follows (in thousands): Three Months Ended Three Months Ended Fixed lease payments $ 211,430 $ 213,007 Variable lease payments 27,479 26,399 Total lease payments $ 238,909 $ 239,406 Amortization of acquired above and below-market leases 1,209 2,362 Total rental revenue $ 240,118 $ 241,768

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings As of March 31, 2019 , 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. Ground Lease Arrangements We are a tenant under ground leases for certain properties. The leases range in term from three to 95 years, with certain leases offering extension options which we assess against relevant economic factors to determine whether we are reasonably certain of exercising or not exercising the option. Lease payments associated with renewal periods that we are reasonably certain will be exercised, if any, are included in the measurement of the corresponding lease liability and right of use asset. The following is a schedule of future minimum lease payments under financing leases and operating leases with initial terms in excess of one year as of March 31, 2019 (in thousands): Financing leases Operating leases (1) Remaining 2019 $ 1,814 $ 23,303 2020 2,619 31,437 2021 2,794 31,629 2022 2,794 29,472 2023 2,794 27,166 2024 2,819 27,183 Thereafter 814,283 648,905 Total minimum lease payments $ 829,917 $ 819,095 Amount representing interest (786,094 ) Amount discounted using incremental borrowing rate (429,238 ) Lease liabilities $ 43,823 $ 389,857 (1) As of March 31, 2019 , the total minimum sublease rentals to be received in the future under non-cancelable subleases is $1.8 billion . During the three months ended March 31, 2019 , we recognized $1.1 million of financing lease costs, of which $0.8 million represented interest and $0.3 million represented amortization of the right-of-use assets. These amounts are included in interest expense, net of interest income and depreciation and amortization in our consolidated statements of operations, respectively. During the three months ended March 31, 2019 , we recognized $ 8.3 million of operating lease costs, which is calculated on a straight-line basis over the remaining lease terms. This amount is included in operating lease rent in our consolidated statements of operations. As of March 31, 2019 , the weighted-average discount rate used to calculate the lease liabilities was 8.44% . As of March 31, 2019 , the weighted-average remaining lease term was 67 years.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	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 contributions. 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, 2019 and 2018 , and selected asset information as of March 31, 2019 and December 31, 2018 , 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, 2019 $ 254,224 $ 50,031 $ 304,255 March 31, 2018 256,405 45,290 301,695 Net income Three months ended: March 31, 2019 $ 21,572 $ 31,197 $ 52,769 March 31, 2018 80,035 33,788 113,823 Total assets As of: March 31, 2019 $ 10,943,516 $ 2,442,258 $ 13,385,774 December 31, 2018 10,481,594 2,269,764 12,751,358 Interest costs for the debt and preferred equity segment include actual costs incurred for borrowings on the 2017 MRA. Interest is imputed on the investments that do not collateralize the 2017 MRA using our weighted average 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, 2019 , and 2018, marketing, general and administrative expenses totaled $26.0 million and $23.5 million respectively. All other expenses, except interest, relate entirely to the real estate assets. There were no transactions between the above two segments.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
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 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. The Company classifies those leases under which the Company is the lessee at lease commencement as finance or operating leases. Leases qualify as finance leases if the lease transfers ownership of the asset at the end of the lease term, the lease grants an option to purchase the asset that we are reasonably certain to exercise, the lease term is for a major part of the remaining economic life of the asset, or the present value of the lease payments exceeds substantially all of the fair value of the asset. Leases that do not qualify as finance leases are deemed to be operating leases. At lease commencement the Company records a lease liability which is measured as the present value of the lease payments and a right of use asset which is measured as the amount of the lease liability and any initial direct costs incurred. The Company applies a discount rate to determine the present value of the lease payments. If the rate implicit in the lease is known, the Company uses that rate. If the rate implicit in the lease is not known, the Company uses a discount rate reflective of the Company’s collateralized borrowing rate given the term of the lease. To determine the discount rate, the Company employs a third party specialist to develop a curve based primarily on the observable borrowing rates of the Company, other REITs, and other corporate borrowers with long-term borrowings. On the statements of operations, operating leases are expensed through operating lease rent while financing leases are expensed through amortization and interest expense. On the balance sheet, financing leases include the amounts previously captioned "Properties under capital lease." When applicable, the Company combines the consideration for lease and non-lease components in the calculation of the value of the lease obligation and right-of-use asset. On a periodic basis, we assess whether there are any indications that the value of our real estate properties may be 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 and depreciation expense is no longer recorded.
Investment in Marketable Securities	Investment in Marketable Securities At acquisition, we designate a security as held-to-maturity, available-for-sale, or trading. As of March 31, 2019 , we did not have any securities designated as held-to-maturity or trading. We account for our available-for-sale 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. The cost of marketable securities sold and the amount reclassified out of accumulated other comprehensive income into earnings is determined using the specific identification method. Any unrealized losses that are determined to be other-than-temporary are recognized in earnings up to their credit component.
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.
Deferred Lease Costs and Lease Classification	Deferred Lease Costs Deferred lease costs consist of incremental fees and direct costs that would not have been incurred if the lease had not been obtained and are amortized on a straight-line basis over the related lease term. Lease Classification Lease classification for leases under which the Company is the lessor is evaluated at lease commencement and leases not classified as sales-type leases or direct financing leases are classified as operating leases. Leases qualify as sales-type leases if the contract includes either transfer of ownership clauses, certain purchase options, a lease term representing a major part of the economic life of the asset, or the present value of the lease payments and residual guarantees provided by the lessee exceeds substantially all of the fair value of the asset. Additionally, leasing an asset so specialized that it is not deemed to have any value to the Company at the end of the lease term may also trigger sales-type lease classification. Leases would qualify as direct financing leases when the present value of the lease payments and residual value guarantees provided by the lessee and unrelated third parties exceeds substantially all of the fair value of the asset and collection of the payments is probable.
Revenue Recognition	Revenue Recognition Rental revenue for operating leases is recognized on a straight-line basis over the term of the lease. Rental revenue recognition commences when the tenant takes possession or controls the physical use of the leased space. In order for the tenant to take possession, the leased space must be substantially ready for its intended use. To determine whether the leased space is substantially ready for its intended use, management evaluates whether we are or the tenant is the owner of tenant improvements for accounting purposes. When management concludes that we are the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of the finished space, which is when such tenant improvements are substantially complete. In certain instances, when management concludes that we are not the owner of tenant improvements, rental revenue recognition begins when the tenant takes possession of or controls the space. When management concludes that we are the owner of tenant improvements for accounting purposes, we record amounts funded to construct the tenant improvements as a capital asset. For these tenant improvements, we record amounts reimbursed by tenants as a reduction of the capital asset. When management concludes that the tenant is the owner of tenant improvements for accounting purposes, we record our contribution towards those improvements as a lease incentive, which is included in deferred costs, net on our consolidated balance sheets and amortized as a reduction to rental revenue on a straight-line basis over the term of the lease. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rents receivable on the consolidated balance sheets. In addition to base rent, our tenants also generally will pay variable rent which represents their pro rata share of increases in real estate taxes and operating expenses for the building over a base year. In some leases, in lieu of paying additional rent based upon increases in building operating expenses, the tenant will pay additional rent based upon increases in the wage rate paid to porters over the porters' wage rate in effect during a base year or increases in the consumer price index over the index value in effect during a base year. In addition, many of our leases contain fixed percentage increases over the base rent to cover escalations. Electricity is most often supplied by the landlord either on a sub-metered basis, or rent inclusion basis (i.e., a fixed fee is included in the rent for electricity, which amount may increase based upon increases in electricity rates or increases in electrical usage by the tenant). Base building services other than electricity (such as heat, air conditioning and freight elevator service during business hours, and base building cleaning) are typically provided at no additional cost, with the tenant paying additional rent only for services which exceed base building services or for services which are provided outside normal business hours. These escalations are based on actual expenses incurred in the prior calendar year. If the expenses in the current year are different from those in the prior year, then during the current year, the escalations will be adjusted to reflect the actual expenses for the current year. Rental revenue is recognized if collectability is probable. If collectability of substantially all of the lease payments is assessed as not probable, any difference between the rental revenue recognized to date and the lease payments that have been collected is recognized as a current-period adjustment to rental revenue. A subsequent change in the assessment of collectability to probable may result in a current-period adjustment to rental revenue for any difference between the rental revenue that would have been recognized if collectability had always been assessed as probable and the rental revenue recognized to date. The Company provides its tenants with certain customary services for lease contracts such as common area maintenance, general security or snow removal. We have elected to combine the nonlease components with the lease components of our operating lease agreements and account for them as a single lease component in accordance with ASC 842. We record a gain on sale of real estate assets when we no longer hold a controlling financial interest in the entity holding the real estate, a contract exists with a third party and that third party has control of the assets acquired. Investment income on debt and preferred equity investments is accrued based on the contractual terms of the instruments and when, in the opinion of management, it is deemed collectible. Some debt and preferred equity investments provide for accrual of interest at specified rates, which differ from current payment terms. Interest is recognized on such loans at the accrual rate subject to management's determination that accrued interest is ultimately collectible, based on the underlying collateral and operations of the borrower. If management cannot make this determination, interest income above the current pay rate is recognized only upon actual receipt. Deferred origination fees, original issue discounts and loan origination costs, if any, are recognized as an adjustment to interest income over the terms of the related investments using the effective interest method. Fees received in connection with loan commitments are also deferred until the loan is funded and are then recognized over the term of the loan as an adjustment to yield. Discounts or premiums associated with the purchase of loans are amortized or accreted into interest income as a yield adjustment on the effective interest method based on expected cash flows through the expected maturity date of the related investment. If we purchase a debt or preferred equity investment at a discount, intend to hold it until maturity and expect to recover the full value of the investment, we accrete the discount into income as an adjustment to yield over the term of the investment. If we purchase a debt or preferred equity investment at a discount with the intention of foreclosing on the collateral, we do not accrete the discount. For debt investments acquired at a discount for credit quality, the difference between contractual cash flows and expected cash flows at acquisition is not accreted. Anticipated exit fees, the collection of which is expected, are also recognized over the term of the loan as an adjustment to yield. Debt and preferred equity investments are placed on a non-accrual status at the earlier of the date at which payments become 90 days past due or when, in the opinion of management, a full recovery of interest income becomes doubtful. Interest income recognition on any non-accrual debt or preferred equity investment is resumed when such non-accrual debt or preferred equity investment becomes contractually current and performance is demonstrated to be resumed. Interest is recorded as income on impaired loans only to the extent cash is received. We may syndicate a portion of the loans that we originate or sell the loans individually. When a transaction meets the criteria for sale accounting, we recognize gain or loss based on the difference between the sales price and the carrying value of the loan sold. Any related unamortized deferred origination fees, original issue discounts, loan origination costs, discounts or premiums at the time of sale are recognized as an adjustment to the gain or loss on sale, which is included in investment income on the consolidated statement of operations. Any fees received at the time of sale or syndication are recognized as part of investment income. Asset management fees are recognized on a straight-line basis over the term of the asset management agreement.
Reserve for Possible Credit Losses	Allowance for Loan Loss and Other Investment Reserves The expense for loan loss and other investment reserves in connection with debt and preferred equity investments is the charge to earnings to adjust the allowance for possible losses to the level that we estimate to be adequate, based on Level 3 data, considering delinquencies, loss experience and collateral quality. The Company evaluates debt and preferred equity investments that are classified as held to maturity for possible impairment or credit deterioration associated with the performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower/sponsor. Quarterly, the Company assigns each loan a risk rating. Based on a 3-point scale, loans are rated “1” through “3,” from less risk to greater risk, which ratings are defined as follows: 1 - Low Risk Assets - Low probability of loss, 2 - Watch List Assets - Higher potential for loss, 3 - High Risk Assets - Loss more likely than not. When it is probable that we will be unable to collect all amounts contractually due, the investment is considered impaired. 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. Debt and preferred equity investments that are classified as 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. We have elected, and may elect in the future, to treat certain of our 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, 2019 , we recorded Federal, state and local tax provisions of $0.8 million . 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.
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 August 2018, the FASB issued Accounting Standard Update (ASU) No. 2018-15, Intangibles - Goodwill and Other- Internal-Use Software (Topic 350-40), Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. The amendments provide guidance on accounting for fees paid when the arrangement includes a software license and align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing costs to develop or obtain internal-use software. The guidance is effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted. 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 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This amendment removed, modified and added the disclosure requirements under Topic 820. The changes are effective for the Company for fiscal years beginning after December 15, 2019. Early adoption is permitted for the removed or modified disclosures with adoption of the additional disclosures upon the effective date. 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 June 2018, the FASB issued ASU No. 2018-07, Compensation - Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting. This amendment provides additional guidance related to share-based payment transactions for acquiring goods or services from nonemployees. The Company adopted this guidance on January 1, 2019 and it did not have a material impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities, and in July 2018, the FASB issued ASU No. 2018-16, Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The amendments in the new standards will permit more flexibility in hedging interest rate risk for both variable rate and fixed rate financial instruments. The standards 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 adopted this guidance on January 1, 2019, and it did not have a material impact on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and in November 2018 issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses. 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’s DPE portfolio and financing lease assets will be subject to this guidance once the Company adopts it. ASU No. 2018-19 excludes operating lease receivables from the scope of this guidance. The Company continues to evaluate 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. In July 2018, the FASB issued ASU No. 2018-10 - Codification Improvements to Topic 842, Leases, and ASU No. 2018-11 - Targeted Improvements. In December 2018, the FASB issued ASU No. 2018-20 - Narrow-Scope Improvements for Lessors and in March 2019 issued ASU No. 2019-01 - Codification Improvements. The Company adopted this guidance on January 1, 2019 using the modified retrospective approach which allows the Company to apply the guidance for the current year presentation and not adjust the prior year numbers. The Company elected the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classification for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. The new guidance applies to the ground leases under which the Company is a lessee. The Company has recognized a new asset and liability - “Right of use asset - operating leases” and “Lease liability - operating leases” - for those leases classified as operating leases under the previous standard. The Company will continue to recognize expense on a straight-line basis for these operating leases. The ground leases that the Company historically reported as “Properties under capital leases” and “Capitalized lease obligations” are now labeled “Right of use asset - financing leases” and “Lease liability - financing leases”. The expense recognition of these leases has not changed. The Company adopted the practical expedient offered in ASU No. 2018-11 that allows lessors to not separate non-lease components from the related lease components under certain conditions. In doing so, the Company has collapsed the line “Escalation and reimbursement revenues” into the “Rental revenue, net” line to reflect adopting this practical expedient. The Company also collapsed the prior year balances to conform to the current year presentation. For future leases, the Company no longer capitalizes internal leasing costs that are not incremental as defined under the new guidance. The Company has recorded an additional expense of approximately $2.2 million related to this change for the first quarter.
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 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. 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.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Tables)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of commercial office properties	As of March 31, 2019 , 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 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 11,676,183 31 24,063,274 94.0 % Retail 7 (2) 325,648 7 283,832 14 609,480 98.9 % Development/Redevelopment 5 486,101 1 — 6 486,101 40.6 % Fee Interest — — 1 — 1 — — % 32 13,198,840 20 11,960,015 52 25,158,855 93.1 % Suburban Office 13 2,295,200 — — 13 2,295,200 90.4 % Retail 1 52,000 — — 1 52,000 100.0 % Development/Redevelopment 1 1,000 — — 1 1,000 — % 15 2,348,200 — — 15 2,348,200 90.6 % Total commercial properties 47 15,547,040 20 11,960,015 67 27,507,055 92.9 % Residential: Manhattan Residential 2 (2) 445,105 9 2,075,896 11 2,521,001 93.3 % Suburban Residential — — — — — — — % Total residential properties 2 445,105 9 2,075,896 11 2,521,001 93.3 % Total portfolio 49 15,992,145 29 14,035,911 78 30,028,056 93.0 % (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, 2019 , 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.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases)	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, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Identified intangible assets (included in other assets): Gross amount $ 266,540 $ 266,540 Accumulated amortization (244,246 ) (241,040 ) Net (1) $ 22,294 $ 25,500 Identified intangible liabilities (included in deferred revenue): Gross amount $ 276,245 $ 276,245 Accumulated amortization (256,010 ) (253,767 ) Net (1) $ 20,235 $ 22,478 (1) As of March 31, 2019 , and December 31, 2018 , no net intangible assets and no 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, 2019 and December 31, 2018 , we held the following marketable securities (in thousands): March 31, 2019 December 31, 2018 Commercial mortgage-backed securities $ 29,406 $ 28,638 Total marketable securities available-for-sale $ 29,406 $ 28,638
Schedules of Concentration of Risk, by Risk Factor	For the three months ended March 31, 2019 , the following properties contributed more than 5.0% of our annualized cash rent, including our share of joint venture annualized cash rent: Property Three Months Ended March 31, 2019 11 Madison Avenue 7.4% 1185 Avenue of the Americas 6.7% 420 Lexington Avenue 6.3% 1515 Broadway 6.0% One Madison Avenue 5.8%

Debt and Preferred Equity Inv_2

Debt and Preferred Equity Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of debt and preferred equity book balance roll forward	Below is a summary of the activity relating to our debt and preferred equity investments for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of year (1) $ 2,099,393 $ 2,114,041 Debt investment originations/accretion (2) 436,819 834,304 Preferred equity investment originations/accretion (2) 3,416 151,704 Redemptions/sales/syndications/amortization (3) (271,387 ) (994,906 ) Net change in loan loss reserves 4,000 (5,750 ) Balance at end of period (1) $ 2,272,241 $ 2,099,393 (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, but did not meet the conditions for sale accounting, are included in other assets and other liabilities on the consolidated balance sheets.
Allowance for Credit Losses on Financing Receivables	The following table is a rollforward of our total loan loss reserves for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of year $ 5,750 $ — Expensed — 6,839 Recoveries — — Charge-offs and reclassifications (4,000 ) (1,089 ) Balance at end of period $ 1,750 $ 5,750
Summary of debt investments	As of March 31, 2019 and December 31, 2018 , we held the following debt investments with an aggregate weighted average current yield of 8.79% at March 31, 2019 (dollars in thousands): Loan Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Maturity (2) Fixed Rate Investments: Mezzanine Loan (3a) $ — $ 1,163,005 $ 215,511 $ 213,185 March 2020 Loan Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Maturity (2) Mezzanine Loan — 15,000 3,500 3,500 September 2021 Mezzanine Loan — 147,000 24,937 24,932 April 2022 Mezzanine Loan — 280,000 37,099 36,585 August 2022 Mezzanine Loan — 318,078 202,184 — June 2023 Mezzanine Loan — 85,097 12,708 12,706 November 2023 Mezzanine Loan — 180,000 30,000 30,000 December 2023 Mezzanine Loan (3b) — 115,000 12,943 12,941 June 2024 Mezzanine Loan — 95,000 30,000 30,000 January 2025 Mezzanine Loan — 1,712,750 55,250 55,250 June 2027 Mezzanine Loan (4) — — — 11,000 Total fixed rate $ — $ 4,110,930 $ 624,132 $ 430,099 Floating Rate Investments: Mezzanine Loan (5) — 45,025 37,500 37,499 January 2019 Mezzanine Loan (3c)(6) — 150,000 15,381 15,333 April 2019 Mezzanine Loan (3d)(6) — — 14,869 14,822 April 2019 Mezzanine Loan (6) — 40,000 19,999 19,986 April 2019 Mezzanine Loan (7) — 265,000 24,993 24,961 April 2019 Mortgage/Jr. Mortgage Participation Loan 39,321 236,424 85,308 84,012 August 2019 Mortgage/Mezzanine Loan — — 19,999 19,999 August 2019 Mortgage/Mezzanine Loan 1,027 — 128,560 154,070 September 2019 Mezzanine Loan — 350,000 34,923 34,886 October 2019 Mortgage/Mezzanine Loan 9,656 64,521 112,886 62,493 January 2020 Mezzanine Loan 509 576,313 94,118 79,164 January 2020 Mortgage/Mezzanine Loan — — 69,310 — March 2020 Mortgage Loan 9,776 — 89,995 88,501 February 2020 Mezzanine Loan 828 324,989 53,917 53,402 March 2020 Mortgage/Mezzanine Loan 8,093 — 230,879 277,694 April 2020 Mortgage/Mezzanine Loan — 62,957 36,991 37,094 June 2020 Mezzanine Loan 7,392 39,649 13,145 12,627 July 2020 Mortgage/Mezzanine Loan — — 83,663 83,449 October 2020 Mezzanine Loan 35,467 375,459 92,055 88,817 November 2020 Mortgage and Mezzanine Loan 31,027 — 101,028 98,804 December 2020 Mortgage and Mezzanine Loan — — 35,295 35,266 December 2020 Jr. Mortgage Participation/Mezzanine Loan — 60,000 15,674 15,665 July 2021 Mezzanine Loan (8) — — — 7,305 Mezzanine Loan (8) — — — 14,998 Mezzanine Loan (8) — — — 21,990 Total floating rate $ 143,096 $ 2,590,337 $ 1,410,488 $ 1,382,837 Total $ 143,096 $ 6,701,267 $ 2,034,620 $ 1,812,936 (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) 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 , and (d) $14.1 million . (4) This loan was sold in 2019. (5) As of January 2019, this loan was in maturity default. No impairment was recorded as the Company believes that the fair value of the property exceeded the carrying amount of the loans. In April 2019, the Company accepted an assignment of the equity interests in the property in lieu of repayment, and marked the assets received and liabilities assumed to fair value. (6) This loan was extended in April 2019. (7) This loan was modified in April 2019. (8) This loan was repaid in 2019.
Summary of preferred equity investments	As of March 31, 2019 and December 31, 2018 , we held the following preferred equity investments with an aggregate weighted average current yield of 8.74% at March 31, 2019 (dollars in thousands): Type March 31, 2019 March 31, 2019 Senior March 31, 2019 (1) December 31, 2018 (1) Mandatory Redemption (2) Preferred Equity $ — $ 272,000 $ 143,009 $ 143,183 April 2021 Preferred Equity — 1,762,761 94,612 143,274 June 2022 Total $ — $ 2,034,761 $ 237,621 $ 286,457 (1) Carrying value is net of deferred origination fees. (2) Represents contractual maturity, excluding any unexercised extension options.

Investments in Unconsolidated_2

Investments in Unconsolidated Joint Ventures (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 : Property Partner Ownership (1) Economic (1) Unaudited Approximate Square Feet Acquisition Date (2) Acquisition (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 11 West 34th Street Private Investor/ 30.00% 30.00% 17,150 December 2010 10,800 280 Park Avenue Vornado Realty Trust 50.00% 50.00% 1,219,158 March 2011 400,000 1552-1560 Broadway (4) Jeff Sutton 50.00% 50.00% 57,718 August 2011 136,550 10 East 53rd Street Canadian Pension Plan Investment Board 55.00% 55.00% 354,300 February 2012 252,500 521 Fifth Avenue (5) Plaza Global 50.50% 50.50% 460,000 November 2012 315,000 21 East 66th Street (6) Private Investors 32.28% 32.28% 13,069 December 2012 75,000 650 Fifth Avenue (7) 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 55 West 46th Street Prudential Real Estate Investors 25.00% 25.00% 347,000 November 2014 295,000 Stonehenge Portfolio (8) Various Various Various 1,439,016 February 2015 36,668 605 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 East 57th Street (9) BlackRock, Inc and Stonehenge Partners 51.00% 41.00% 290,482 October 2016 170,000 One Vanderbilt (10) National Pension Service of Korea/Hines Interest LP 71.01% 71.01% — January 2017 3,310,000 Worldwide Plaza RXR Realty / New York REIT / Private Investor 24.35% 24.35% 2,048,725 October 2017 1,725,000 1515 Broadway Allianz Real Estate of America 56.87% 56.87% 1,750,000 November 2017 1,950,000 2 Herald Square Israeli Institutional Investor 51.00% 51.00% 369,000 November 2018 266,000 (1) Ownership interest and economic interest represent the Company's interests in the joint venture as of March 31, 2019 . 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 asset value of the property or properties 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. We recorded our 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 joint venture. (4) The acquisition 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. (5) In March 2019, we, along with our joint venture partner, entered into an agreement to sell this property. (6) 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. (7) 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. (8) In February 2019, we, together with our joint venture partner, closed on the sale of one property from the Stonehenge Portfolio. This sale is further described under Sale of Joint Venture Interest of Properties below. In May 2019, we closed on the sale of our interest in one additional property from the Stonehenge Portfolio. (9) In October 2016, we sold a 49% interest in this property to an investment account managed by BlackRock, Inc. Our 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. Our joint venture with Stonehenge remains consolidated resulting in the combined 51% interest being shown within investments in unconsolidated joint ventures on our balance sheet. (10) The partners' ownership interest in the joint venture is based on their capital contributions, up to an aggregate maximum of 29.0% . As of March 31, 2019 the total of the two partners' ownership interests based on equity contributed was 28.17% . As of March 31, 2019 and December 31, 2018 , the carrying value for acquisition, development and construction arrangements were as follows (dollars in thousands): Loan Type March 31, 2019 December 31, 2018 Maturity Date Mezzanine Loan (1) 44,824 44,357 February 2022 $ 44,824 $ 44,357 (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. In May 2019, the Company purchased a majority and controlling interest in the underlying property.
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, 2019 and December 31, 2018 , respectively, are as follows (dollars in thousands): Property Economic (1) Maturity Date Interest Rate (2) March 31, 2019 December 31, 2018 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 % 500,000 500,000 1515 Broadway 56.87 % March 2025 3.93 % 851,492 855,876 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 % 99,311 99,828 Worldwide Plaza 24.35 % November 2027 3.98 % 1,200,000 1,200,000 Stonehenge Portfolio (5) (6) Various Various 4.20 % 320,047 321,076 Property Economic (1) Maturity Date Interest Rate (2) March 31, 2019 December 31, 2018 Total fixed rate debt $ 5,660,178 $ 5,666,108 Floating Rate Debt: 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 10 East 53rd Street 55.00 % February 2020 L+ 2.25 % 170,000 170,000 1552 Broadway 50.00 % October 2020 L+ 2.65 % 195,000 195,000 55 West 46th Street (7) 25.00 % November 2020 L+ 2.13 % 188,939 185,569 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 % 359,705 360,000 One Vanderbilt (8) 71.01 % September 2021 L+ 2.75 % 375,000 375,000 2 Herald Square (9) 51.00 % November 2021 L+ 1.55 % 133,565 133,565 605 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 % 1,552 1,571 131-137 Spring Street (10) — 141,000 103 East 86th Street (11) — 38,000 Total floating rate debt $ 3,211,761 $ 3,387,705 Total joint venture mortgages and other loans payable $ 8,871,939 $ 9,053,813 Deferred financing costs, net (111,606 ) (103,191 ) Total joint venture mortgages and other loans payable, net $ 8,760,333 $ 8,950,622 (1) Economic interest represents the Company's interests in the joint venture as of March 31, 2019 . 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, 2019 , 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 $133.6 million , $53.8 million , and $132.6 million in fixed-rate mortgages that mature in August 2019, June 2024, and April 2028, respectively. (6) In May 2019, we closed on the sale of our interest in one property from the Stonehenge Portfolio. (7) This loan has a committed amount of $195.0 million , of which $6.1 million was unfunded as of March 31, 2019 . (8) This loan is a $1.75 billion construction facility, with reductions in interest cost 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. (9) This loan has a committed amount of $150.0 million . (10) In January 2019, we closed on the sale of our interest in the property. (11) In February 2019, we, along with our joint venture partner, closed on the sale of the property.
Schedule of combined balance sheets for the unconsolidated joint ventures	The combined balance sheets for the unconsolidated joint ventures, at March 31, 2019 and December 31, 2018 are as follows (in thousands): March 31, 2019 December 31, 2018 Assets (1) Commercial real estate property, net $ 14,362,952 $ 14,347,673 Cash and restricted cash 370,832 381,301 Tenant and other receivables, related party receivables, and deferred rents receivable 321,696 273,141 Debt and preferred equity investments, net 44,824 44,357 Other assets 2,191,441 2,187,166 Total assets $ 17,291,745 $ 17,233,638 Liabilities and equity (1) Mortgages and other loans payable, net $ 8,760,333 $ 8,950,622 Deferred revenue/gain 1,620,437 1,660,838 Lease liabilities 901,808 637,168 Other liabilities 341,134 309,145 Equity 5,668,033 5,675,865 Total liabilities and equity $ 17,291,745 $ 17,233,638 Company's investments in unconsolidated joint ventures $ 3,055,368 $ 3,019,020 (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, from acquisition date through the three months ended March 31, 2019 and 2018 , are as follows (in thousands): Three Months Ended March 31, 2019 2018 Total revenues $ 307,519 $ 320,941 Operating expenses 54,124 59,773 Operating lease rent 5,901 4,393 Real estate taxes 54,236 57,027 Interest expense, net of interest income 96,623 89,741 Amortization of deferred financing costs 5,216 5,116 Depreciation and amortization 104,331 105,080 Total expenses 320,431 321,130 Net loss before gain on sale (1) $ (12,912 ) $ (189 ) Company's equity in net (loss) income from unconsolidated joint ventures (1) $ (5,234 ) $ 4,036 (1) The combined statements of operations and the Company's equity in net (loss) 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
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, 2019 : Property Ownership Interest Disposition Date Gross Asset Valuation (in thousands) (1) Gain on Sale (in thousands) (2) 131-137 Spring Street 20.00% January 2019 $ 216,000 $ 17,660 103 East 86th Street (3) 1.00% February 2019 90,500 19 (1) Represents implied gross valuation for the joint venture or sales price of the property. (2) Represents our share of the gain. Gain amounts do not include adjustments for expenses recorded in subsequent periods. (3) Property was part of the Stonehenge Portfolio.

Deferred Costs (Tables)

Deferred Costs (Tables)	3 Months Ended
	Mar. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of components of deferred costs	Deferred costs at March 31, 2019 and December 31, 2018 consisted of the following (in thousands): March 31, 2019 December 31, 2018 Deferred leasing costs $ 463,521 $ 453,833 Less: accumulated amortization (251,906 ) (244,723 ) Deferred costs, net $ 211,615 $ 209,110

Mortgages and Other Loans Pay_2

Mortgages and Other Loans Payable (Tables)	3 Months Ended
	Mar. 31, 2019
Mortgages and Other Loans Payable
Schedule of first mortgages and other loans payable collateralized by the respective properties and assignment of leases	The first mortgages and other loans payable collateralized by the respective properties and assignment of leases or debt investments at March 31, 2019 and December 31, 2018 , respectively, were as follows (dollars in thousands): Property Maturity Date Interest Rate (1) March 31, 2019 December 31, 2018 Fixed Rate Debt: 762 Madison Avenue February 2022 5.00 % 771 771 100 Church Street July 2022 4.68 % 212,463 213,208 420 Lexington Avenue October 2024 3.99 % 300,000 300,000 400 East 58th Street (2) November 2026 3.00 % 39,724 39,931 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 % 35,634 35,807 315 West 33rd Street February 2027 4.17 % 250,000 250,000 Total fixed rate debt $ 1,388,592 $ 1,389,717 Floating Rate Debt: FHLB Facility May 2019 L+ 0.27 % 13,000 13,000 2017 Master Repurchase Agreement June 2019 L+ 2.34 % 300,000 300,000 FHLB Facility December 2019 L+ 0.18 % 14,500 14,500 FHLB Facility January 2020 L+ 0.26 % 10,000 — 133 Greene Street August 2020 L+ 2.00 % 15,523 15,523 609 Fifth Avenue March 2021 L+ 2.40 % 49,872 — 185 Broadway (4) November 2021 L+ 2.85 % 111,869 111,869 712 Madison Avenue December 2021 L+ 2.50 % 28,000 28,000 115 Spring Street September 2023 L+ 3.40 % 65,550 65,550 719 Seventh Avenue September 2023 L+ 1.20 % 50,000 50,000 Total floating rate debt $ 658,314 $ 598,442 Total mortgages and other loans payable $ 2,046,906 $ 1,988,159 Deferred financing costs, net of amortization (28,345 ) (26,919 ) Total mortgages and other loans payable, net $ 2,018,561 $ 1,961,240 (1) Interest rate as of March 31, 2019 , 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) This loan is a $225.0 million construction facility, with reductions in interest cost based on meeting certain conditions, and has an initial three -year term with two one -year extension options. Advances under the loan are subject to incurred costs and funded equity requirements.

Corporate Indebtedness (Tables)

Corporate Indebtedness (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 , respectively, by scheduled maturity date (amounts in thousands): Issuance March 31, March 31, December 31, Interest Rate (1) Initial Term (in Years) Maturity Date March 16, 2010 (2) $ 250,000 $ 250,000 $ 250,000 7.75 % 10 March 2020 August 7, 2018 (3) (4) 350,000 350,000 350,000 L+ 0.98 % 3 August 2021 October 5, 2017 (3) 500,000 499,616 499,591 3.25 % 5 October 2022 November 15, 2012 (5) 300,000 303,918 304,168 4.50 % 10 December 2022 December 17, 2015 (2) 100,000 100,000 100,000 4.27 % 10 December 2025 $ 1,500,000 $ 1,503,534 $ 1,503,759 Deferred financing costs, net (8,044 ) (8,545 ) $ 1,500,000 $ 1,495,490 $ 1,495,214 (1) Interest rate as of March 31, 2019 , taking into account interest rate hedges in effect during the period. Floating rate notes are presented with the stated spread over 3-month LIBOR, unless otherwise specified. 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 and the Operating Partnership as co-obligors. (3) Issued by the Operating Partnership with the Company as the guarantor. (4) Beginning on August 8, 2019 and at any time thereafter, the notes are subject to redemption at the Company's option, in whole but not in part, at a redemption price equal to 100% of the principal amount of the notes, plus unpaid accrued interest thereon to the redemption date. (5) In October 2017, the Company and the Operating Partnership 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	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, 2019 , including as-of-right extension options and put options, were as follows (in thousands): Scheduled Amortization Mortgages and Other Loans Payable Revolving Credit Facility Unsecured Term Loans Trust Preferred Securities Senior Unsecured Notes Total Joint Venture Debt Remaining 2019 $ 5,143 $ 27,500 $ — $ — $ — $ — $ 32,643 $ 112,359 2020 11,118 325,523 — — — 250,000 586,641 251,433 2021 11,638 189,741 — — — 350,000 551,379 522,359 2022 9,430 198,555 — — — 800,000 1,007,985 220,810 2023 7,301 115,550 790,000 1,300,000 — — 2,212,851 277,996 Thereafter 9,291 1,136,116 — 200,000 100,000 100,000 1,545,407 2,430,198 $ 53,921 $ 1,992,985 $ 790,000 $ 1,500,000 $ 100,000 $ 1,500,000 $ 5,936,906 $ 3,815,155
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, 2019 2018 Interest expense before capitalized interest $ 60,810 $ 54,132 Interest on financing leases 804 786 Interest capitalized (10,509 ) (6,686 ) Interest income (580 ) (316 ) Interest expense, net $ 50,525 $ 47,916

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Schedule of amounts due from/to related parties	Amounts due from joint ventures and related parties at March 31, 2019 and December 31, 2018 consisted of the following (in thousands): March 31, 2019 December 31, 2018 Due from joint ventures $ 20,723 $ 18,655 Other 8,735 9,378 Related party receivables $ 29,458 $ 28,033

Noncontrolling Interests on t_2

Noncontrolling Interests on the Company's Consolidated Financial Statements (Tables)	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Schedule of Noncontrolling Interest	Below is a summary of the activity relating to the noncontrolling interests in the Operating Partnership for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of period $ 387,805 $ 461,954 Distributions (3,643 ) (15,000 ) Issuance of common units 14,135 23,655 Redemption of common units (16,143 ) (60,718 ) Net income 2,278 12,216 Accumulated other comprehensive income allocation (1,003 ) (66 ) Fair value adjustment 28,932 (34,236 ) Balance at end of period $ 412,361 $ 387,805
Schedule of Preferred Unit Activity	Below is a summary of the preferred units of limited partnership interest in the Operating Partnership as of March 31, 2019 : Issuance Number of Units Authorized Number of Units Issued Dividends Per Unit (1) Liquidation Preference Per Unit (2) Conversion Price Per Unit (3) Date of Issuance 4.50% Series G (4) 1,902,000 1,902,000 $ 1.1250 $ 25.00 $ 88.50 January 2012 7.00% Series F 60 60 $ 70.0000 $ 1,000.00 $ 29.12 January 2007 3.50% Series K 700,000 563,954 $ 0.8750 $ 25.00 $ 134.67 August 2014 4.00% Series L 500,000 378,634 $ 1.0000 $ 25.00 — August 2014 3.75% Series M 1,600,000 1,600,000 $ 0.9375 $ 25.00 — February 2015 3.00% Series N (5) 552,303 552,303 $ 0.7500 $ 25.00 — June 2015 Series O (6) 1 1 (6 ) (6 ) — June 2015 4.00% Series P 200,000 200,000 $ 1.0000 $ 25.00 — July 2015 3.50% Series Q 268,000 268,000 $ 0.8750 $ 25.00 $ 148.95 July 2015 3.50% Series R 400,000 400,000 $ 0.8750 $ 25.00 $ 154.89 August 2015 4.00% Series S 1,077,280 1,077,280 $ 1.0000 $ 25.00 — August 2015 2.75% Series T 230,000 230,000 $ 0.6875 $ 25.00 $ 119.02 March 2016 4.50% Series U (7) 680,000 680,000 $ 1.1250 $ 25.00 — March 2016 3.50% Series A (8) 109,161 109,161 $ 35.0000 $ 1,000.00 — August 2015 (1) Dividends are cumulative, subject to certain provisions. (2) Units are redeemable at any time at par for cash at the option of the unitholder unless otherwise specified. (3) If applicable, 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) the amount shown in the table. (4) Common units of limited partnership interest in the Operating Partnership issued in a conversion 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. (5) All of the outstanding units were redeemed at par for cash by the unitholder during the three months ended March 31, 2019 . (6) The holder of the Series O preferred unit is entitled to quarterly dividends in an amount calculated as (i) 1,350 multiplied by (ii) the current distribution per common unit of limited partnership in SL Green Operating Partnership. The holder has the right to require the Operating Partnership to repurchase the Series O unit for cash at a price that is determined based on the closing price of the Company's common stock at the time such right is exercised. The unit's liquidation preference is the fair market value of the unit at the time of a liquidation event. (7) The annual dividend is subject to reduction upon the occurrence of certain circumstances. The minimum annual dividend is $0.75 per unit. (8) Issued through a consolidated subsidiary. The units 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, 2019 , no Subsidiary Series B Preferred Units have been issued. Below is a summary of the activity relating to the preferred units in the Operating Partnership for the three months ended March 31, 2019 and the twelve months ended December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Balance at beginning of period $ 300,427 $ 301,735 Issuance of preferred units — — Redemption of preferred units (15,142 ) (1,308 ) Balance at end of period $ 285,285 $ 300,427

Stockholders' Equity of the C_2

Stockholders' Equity of the Company (Tables)	3 Months Ended
	Mar. 31, 2019
Stockholders' Equity Note [Abstract]
Class of Treasury Stock	At March 31, 2019 , repurchases executed 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 Year ended 2017 8,342,411 $101.64 8,342,411 Year ended 2018 9,744,911 $96.22 18,087,322 First quarter 2019 397,783 $86.07 18,485,105
Schedule of Common Stock Issued and Proceeds Received Dividend Reinvestments	The following table summarizes SL Green common stock issued, and proceeds received from dividend reinvestments and/or stock purchases under the DRSPP for the three months ended March 31, 2019 and 2018 , respectively (dollars in thousands): Three Months Ended March 31, 2019 2018 Shares of common stock issued 540 447 Dividend reinvestments/stock purchases under the DRSPP $ 47 $ 42
Schedule of Earnings Per Share	SL Green's earnings per share for the three months ended March 31, 2019 and 2018 are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SL Green common stockholders $ 43,792 $ 101,766 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net income attributable to SL Green common stockholders (numerator for basic earnings per share) $ 43,668 $ 101,615 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Add back: Effect of dilutive securities (redemption of units to common shares) 2,278 5,272 Income attributable to SL Green common stockholders (numerator for diluted earnings per share) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic Shares: Weighted average common stock outstanding 83,313 90,520 Effect of Dilutive Securities: Operating Partnership units redeemable for common shares 4,333 4,683 Stock-based compensation plans 164 53 Diluted weighted average common stock outstanding 87,810 95,256

Partners' Capital of the Oper_2

Partners' Capital of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 and 2018 , respectively, are computed as follows (in thousands): Three Months Ended March 31, Numerator 2019 2018 Basic Earnings: Income attributable to SLGOP common unitholders $ 46,070 $ 107,038 Less: distributed earnings allocated to participating securities (124 ) (109 ) Less: undistributed earnings allocated to participating securities — (42 ) Net Income attributable to SLGOP common unitholders (numerator for basic earnings per unit) $ 45,946 $ 106,887 Add back: distributed earnings allocated to participating securities 124 109 Add back: undistributed earnings allocated to participating securities — 42 Income attributable to SLGOP common unitholders (numerator for diluted earnings per unit) $ 46,070 $ 107,038 Three Months Ended March 31, Denominator 2019 2018 Basic units: Weighted average common units outstanding 87,646 95,203 Effect of Dilutive Securities: Stock-based compensation plans 164 53 Diluted weighted average common units outstanding 87,810 95,256

Share-based Compensation (Table

Share-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
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	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, 2019 and the year ended December 31, 2018 . There were no grants during the three months ended March 31, 2019 . March 31, 2019 December 31, 2018 Dividend yield none 2.85 % Expected life zero 3.5 years Risk-free interest rate none 2.48 % Expected stock price volatility none 22.00 %
Summary of the status of stock options and changes during the period	A summary of the status of the Company's stock options as of March 31, 2019 and December 31, 2018 , and changes during the three months ended March 31, 2019 and year ended December 31, 2018 are as follows: March 31, 2019 December 31, 2018 Options Outstanding Weighted Average Exercise Price Options Outstanding Weighted Average Exercise Price Balance at beginning of period 1,137,017 $ 103.54 1,548,719 $ 101.48 Granted — — 6,000 97.91 Exercised — — (316,302 ) 90.22 Lapsed or canceled (5,999 ) 110.56 (101,400 ) 113.22 Balance at end of period 1,131,018 $ 103.50 1,137,017 $ 103.54 Options exercisable at end of period 994,045 $ 103.00 783,035 $ 101.28 Total fair value of options granted during the period $ — $ 84,068
Summary of restricted stock and charges during the period	A summary of the Company's restricted stock as of March 31, 2019 and December 31, 2018 and charges during the three months ended March 31, 2019 and the year ended December 31, 2018 , are as follows: March 31, 2019 December 31, 2018 Balance at beginning of period 3,452,016 3,298,216 Granted 6,000 162,900 Canceled (5,950 ) (9,100 ) Balance at end of period 3,452,066 3,452,016 Vested during the period 110,274 92,114 Compensation expense recorded $ 3,411,841 $ 12,757,704 Total fair value of restricted stock granted during the period $ 474,480 $ 13,440,503

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Schedule of accumulated other comprehensive income (loss)	The following tables set forth the changes in accumulated other comprehensive (loss) income by component as of March 31, 2019 (in thousands): Net unrealized gain (loss) on derivative instruments ( 1 ) SL Green’s share of joint venture net unrealized gain (loss) on derivative instruments ( 2 ) Net unrealized gain on marketable securities Total Balance at December 31, 2018 $ 9,716 $ 4,299 $ 1,093 $ 15,108 Other comprehensive (loss) income before reclassifications (11,864 ) (6,972 ) 731 (18,105 ) Amounts reclassified from accumulated other comprehensive income (530 ) (478 ) — (1,008 ) Balance at March 31, 2019 $ (2,678 ) $ (3,151 ) $ 1,824 $ (4,005 ) (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, 2019 and December 31, 2018 , 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 $0.8 million and $1.3 million , respectively. (2) Amount reclassified from accumulated other comprehensive income (loss) is included in equity in net (loss) income from unconsolidated joint ventures in the respective consolidated statements of operations.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair value measurements, recurring and nonrecurring	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, 2019 and December 31, 2018 (in thousands): March 31, 2019 Total Level 1 Level 2 Level 3 Assets: Marketable securities $ 29,406 $ — $ 29,406 $ — Interest rate cap and swap agreements (included in other assets) $ 13,644 $ — $ 13,644 $ — Liabilities: Interest rate cap and swap agreements (included in other liabilities) $ 15,644 $ — $ 15,644 $ — December 31, 2018 Total Level 1 Level 2 Level 3 Assets: Marketable securities $ 28,638 $ — $ 28,638 $ — Interest rate cap and swap agreements (included in other assets) $ 18,676 $ — $ 18,676 $ — Liabilities: Interest rate cap and swap agreements (included in other liabilities) $ 7,663 $ — $ 7,663 $ —
Fair value, by balance sheet grouping	The following table provides the carrying value and fair value of these financial instruments as of March 31, 2019 and December 31, 2018 (in thousands): March 31, 2019 December 31, 2018 Carrying Value (1) Fair Value Carrying Value (1) Fair Value Debt and preferred equity investments $ 2,272,241 (2) $ 2,099,393 (2) Fixed rate debt $ 3,542,126 $ 3,627,127 $ 3,543,476 $ 3,230,127 Variable rate debt 2,398,314 2,404,641 2,048,442 2,057,966 $ 5,940,440 $ 6,031,768 $ 5,591,918 $ 5,288,093 (1) Amounts exclude net deferred financing costs. (2) At March 31, 2019 , debt and preferred equity investments had an estimated fair value ranging between $2.3 billion and $2.5 billion . At December 31, 2018 , debt and preferred equity investments had an estimated fair value ranging between $2.1 billion and $2.3 billion .

Financial Instruments_ Deriva_2

Financial Instruments: Derivatives and Hedging (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of notional and fair value of derivative financial instruments and foreign currency hedges	The following table summarizes the notional value at inception and fair value of our consolidated derivative financial instruments at March 31, 2019 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 (dollars in thousands). Notional Value Strike Rate Effective Date Expiration Date Balance Sheet Location Fair Value Interest Rate Cap $ 137,500 4.000 % September 2017 September 2019 Other Assets $ — Interest Rate Cap 111,869 3.500 % November 2018 December 2019 Other Assets — Interest Rate Swap 100,000 1.928 % December 2017 November 2020 Other Assets 574 Interest Rate Swap 100,000 1.934 % December 2017 November 2020 Other Assets 565 Interest Rate Cap 85,000 4.000 % March 2019 March 2021 Other Assets 1 Interest Rate Swap 200,000 1.131 % July 2016 July 2023 Other Assets 8,418 Interest Rate Swap 100,000 1.161 % July 2016 July 2023 Other Assets 4,086 Interest Rate Swap 150,000 2.696 % January 2019 January 2024 Other Liabilities (3,688 ) Interest Rate Swap 150,000 2.721 % January 2019 January 2026 Other Liabilities (5,078 ) Interest Rate Swap 200,000 2.740 % January 2019 January 2026 Other Liabilities (6,878 ) $ (2,000 )
Schedule of effect of derivative financial instruments on consolidated statements of income	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, 2019 and 2018 , respectively (in thousands): Amount of Gain (Loss) Location of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Income Amount of Gain (Loss) Three Months Ended March 31, Three Months Ended March 31, Derivative 2019 2018 2019 2018 Interest Rate Swaps/Caps $ (11,963 ) $ 7,282 Interest expense $ 535 $ (338 ) Share of unconsolidated joint ventures' derivative instruments (5,369 ) 3,313 Equity in net income from unconsolidated joint ventures 368 (90 ) $ (17,332 ) $ 10,595 $ 903 $ (428 )

Rental Income (Tables)

Rental Income (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lessor, Operating Lease, Payments to be Received, Maturity	Approximate future minimum rents to be received over the next five years and thereafter for non-cancelable operating leases in effect at March 31, 2019 for the consolidated properties, including consolidated joint venture properties, and our share of unconsolidated joint venture properties, are as follows (in thousands): Consolidated Properties Unconsolidated Properties Remaining 2019 $ 638,682 $ 265,578 2020 801,572 385,998 2021 654,113 392,375 2022 591,562 373,353 2023 527,679 344,592 2024 487,263 315,338 Thereafter 3,068,298 1,854,001 $ 6,769,169 $ 3,931,235
Schedule of Future Minimum Rental Payments for Operating Leases	As of December 31, 2018 , under ASC 840, approximate future minimum rents to be received over the next five years and thereafter for non-cancelable operating leases for the consolidated properties, including consolidated joint venture properties, and our share of unconsolidated joint venture properties are as follows (in thousands): Consolidated Properties Unconsolidated Properties 2019 $ 830,336 $ 348,060 2020 765,610 375,228 2021 625,956 380,886 2022 562,250 348,222 2023 500,499 333,501 Thereafter 3,272,014 2,098,995 $ 6,556,665 $ 3,884,892
Operating Lease, Lease Income	The components of lease revenues were as follows (in thousands): Three Months Ended Three Months Ended Fixed lease payments $ 211,430 $ 213,007 Variable lease payments 27,479 26,399 Total lease payments $ 238,909 $ 239,406 Amortization of acquired above and below-market leases 1,209 2,362 Total rental revenue $ 240,118 $ 241,768

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Finance lease, liability, maturity	The following is a schedule of future minimum lease payments under financing leases and operating leases with initial terms in excess of one year as of March 31, 2019 (in thousands): Financing leases Operating leases (1) Remaining 2019 $ 1,814 $ 23,303 2020 2,619 31,437 2021 2,794 31,629 2022 2,794 29,472 2023 2,794 27,166 2024 2,819 27,183 Thereafter 814,283 648,905 Total minimum lease payments $ 829,917 $ 819,095 Amount representing interest (786,094 ) Amount discounted using incremental borrowing rate (429,238 ) Lease liabilities $ 43,823 $ 389,857 (1) As of March 31, 2019 , the total minimum sublease rentals to be received in the future under non-cancelable subleases is $1.8 billion .
Schedule of future minimum rental payments for operating leases	The following is a schedule of future minimum lease payments under financing leases and operating leases with initial terms in excess of one year as of March 31, 2019 (in thousands): Financing leases Operating leases (1) Remaining 2019 $ 1,814 $ 23,303 2020 2,619 31,437 2021 2,794 31,629 2022 2,794 29,472 2023 2,794 27,166 2024 2,819 27,183 Thereafter 814,283 648,905 Total minimum lease payments $ 829,917 $ 819,095 Amount representing interest (786,094 ) Amount discounted using incremental borrowing rate (429,238 ) Lease liabilities $ 43,823 $ 389,857 (1) As of March 31, 2019 , the total minimum sublease rentals to be received in the future under non-cancelable subleases is $1.8 billion .

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of selected results of operations and selected asset information	Selected consolidated results of operations for the three months ended March 31, 2019 and 2018 , and selected asset information as of March 31, 2019 and December 31, 2018 , 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, 2019 $ 254,224 $ 50,031 $ 304,255 March 31, 2018 256,405 45,290 301,695 Net income Three months ended: March 31, 2019 $ 21,572 $ 31,197 $ 52,769 March 31, 2018 80,035 33,788 113,823 Total assets As of: March 31, 2019 $ 10,943,516 $ 2,442,258 $ 13,385,774 December 31, 2018 10,481,594 2,269,764 12,751,358

Organization and Basis of Pre_3

Organization and Basis of Presentation - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Service Corporation
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	95.00%
SL Green Management LLC
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%
SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	4.87%	4.70%

Organization and Basis of Pre_4

Organization and Basis of Presentation - Schedule of Commercial Office Properties (Details) $ in Billions	3 Months Ended
	Mar. 31, 2019USD ($)ft²buildingshares
Real estate properties
Number of Properties | building	78
Approximate Square Feet unaudited (sqft)	30,028,056
Weighted Average Occupancy unaudited (as a percent)	93.00%
Debt and preferred equity investments including investments held by unconsolidated joint ventures | $	$ 2.3
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	67
Approximate Square Feet unaudited (sqft)	27,507,055
Weighted Average Occupancy unaudited (as a percent)	92.90%
Residential
Real estate properties
Number of Properties | building	11
Approximate Square Feet unaudited (sqft)	2,521,001
Weighted Average Occupancy unaudited (as a percent)	93.30%
Managed office properties
Real estate properties
Approximate Square Feet unaudited (sqft)	2,100,000
Consolidated properties
Real estate properties
Number of Properties | building	49
Approximate Square Feet unaudited (sqft)	15,992,145
Consolidated properties | Commercial properties
Real estate properties
Number of Properties | building	47
Approximate Square Feet unaudited (sqft)	15,547,040
Consolidated properties | Residential
Real estate properties
Number of Properties | building	2
Approximate Square Feet unaudited (sqft)	445,105
Unconsolidated properties
Real estate properties
Number of Properties | building	29
Approximate Square Feet unaudited (sqft)	14,035,911
Unconsolidated properties | Commercial properties
Real estate properties
Number of Properties | building	20
Approximate Square Feet unaudited (sqft)	11,960,015
Unconsolidated properties | Residential
Real estate properties
Number of Properties | building	9
Approximate Square Feet unaudited (sqft)	2,075,896
Manhattan
Real estate properties
Number of Properties | building	52
Approximate Square Feet unaudited (sqft)	25,158,855
Weighted Average Occupancy unaudited (as a percent)	93.10%
Manhattan | Office
Real estate properties
Number of Properties | building	31
Approximate Square Feet unaudited (sqft)	24,063,274
Weighted Average Occupancy unaudited (as a percent)	94.00%
Manhattan | Retail
Real estate properties
Number of Properties | building	14
Approximate Square Feet unaudited (sqft)	609,480
Weighted Average Occupancy unaudited (as a percent)	98.90%
Manhattan | Development/Redevelopment
Real estate properties
Number of Properties | building	6
Approximate Square Feet unaudited (sqft)	486,101
Weighted Average Occupancy unaudited (as a percent)	40.60%
Manhattan | Fee Interest
Real estate properties
Number of Properties | building	1
Approximate Square Feet unaudited (sqft)	0
Weighted Average Occupancy unaudited (as a percent)	0.00%
Manhattan | Residential
Real estate properties
Number of Properties | building	11
Approximate Square Feet unaudited (sqft)	2,521,001
Weighted Average Occupancy unaudited (as a percent)	93.30%
Manhattan | Consolidated properties
Real estate properties
Number of Properties | building	32
Approximate Square Feet unaudited (sqft)	13,198,840
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	7
Approximate Square Feet unaudited (sqft)	325,648
Manhattan | Consolidated properties | Development/Redevelopment
Real estate properties
Number of Properties | building	5
Approximate Square Feet unaudited (sqft)	486,101
Manhattan | Consolidated properties | Fee Interest
Real estate properties
Number of Properties | building	0
Approximate Square Feet unaudited (sqft)	0
Manhattan | Consolidated properties | Residential
Real estate properties
Number of Properties | building	2
Approximate Square Feet unaudited (sqft)	445,105
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	20
Approximate Square Feet unaudited (sqft)	11,960,015
Manhattan | Unconsolidated properties | Office
Real estate properties
Number of Properties | building	11
Approximate Square Feet unaudited (sqft)	11,676,183
Manhattan | Unconsolidated properties | Retail
Real estate properties
Number of Properties | building	7
Approximate Square Feet unaudited (sqft)	283,832
Manhattan | Unconsolidated properties | Development/Redevelopment
Real estate properties
Number of Properties | building	1
Approximate Square Feet unaudited (sqft)	0
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	9
Approximate Square Feet unaudited (sqft)	2,075,896
Suburban
Real estate properties
Number of Properties | building	15
Approximate Square Feet unaudited (sqft)	2,348,200
Weighted Average Occupancy unaudited (as a percent)	90.60%
Suburban | Office
Real estate properties
Number of Properties | building	13
Approximate Square Feet unaudited (sqft)	2,295,200
Weighted Average Occupancy unaudited (as a percent)	90.40%
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	1
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	15
Approximate Square Feet unaudited (sqft)	2,348,200
Suburban | Consolidated properties | Office
Real estate properties
Number of Properties | building	13
Approximate Square Feet unaudited (sqft)	2,295,200
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	0
Approximate Square Feet unaudited (sqft)	0
Suburban | Unconsolidated properties | Office
Real estate properties
Number of Properties | building	0
Approximate Square Feet unaudited (sqft)	0
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	0
Approximate Square Feet unaudited (sqft)	0
Suburban | Unconsolidated properties | Residential
Real estate properties
Number of Properties | building	0
Approximate Square Feet unaudited (sqft)	0

Significant Accounting Polici_4

Significant Accounting Policies - Investments in Commercial Real Estate Properties (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Investment in Commercial Real Estate Properties
Rental revenue from amortization of acquired leases	$ 1,200	$ 2,400
Identified intangible assets (included in other assets):
Gross amount	266,540		$ 266,540
Accumulated amortization	(244,246)		(241,040)
Net	22,294		25,500
Identified intangible liabilities (included in deferred revenue):
Gross amount	276,245		276,245
Accumulated amortization	(256,010)		(253,767)
Net	$ 20,235		$ 22,478
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 Polici_5

Significant Accounting Policies - Investment in Marketable Securities (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Investment in Marketable Securities
Marketable securities	$ 29,406,000	$ 28,638,000
Fair Value
Investment in Marketable Securities
Marketable securities	29,406,000	28,638,000
Equity marketable securities
Investment in Marketable Securities
Cost basis	0	0
Commercial mortgage-backed securities
Investment in Marketable Securities
Marketable securities	29,406,000	28,638,000
Cost basis	$ 27,500,000	$ 27,500,000

Significant Accounting Polici_6

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

Significant Accounting Polici_7

Significant Accounting Policies - Revenue Recognition/Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income taxes
Federal, state and local tax provision	$ 0.8	$ 0.5

Significant Accounting Polici_8

Significant Accounting Policies - Concentrations of Credit Risk/Accounting Standards Updates (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2019USD ($)Tenant	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Concentration of Credit Risk
Increase in total assets	[1]	$ 13,385,774		$ 12,751,358
Increase in total liabilities	[1]	$ 6,843,805		$ 6,115,271
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 | 11 Madison Avenue | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		7.40%
Annualized rent | 420 Lexington Avenue | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		6.30%
Annualized rent | 1185 Avenue of the Americas | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		6.70%
Annualized rent | 1515 Broadway | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		6.00%
Annualized rent | 1 Madison Ave | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		5.80%
Tenant 1 | Annualized rent | Customer concentration
Concentration of Credit Risk
Percentage of concentration (percent)		8.20%
Accounting Standards Update 2016-02
Concentration of Credit Risk
Lease cost		$ 2,200
Minimum | Accounting Standards Update 2016-02
Concentration of Credit Risk
Increase in total liabilities			$ 400,000
Maximum | Accounting Standards Update 2016-02
Concentration of Credit Risk
Increase in total liabilities			$ 500,000
[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: $110.0 million and $110.0 million of land, $0.3 billion and $0.3 billion of building and improvements, $0.0 million and $2.0 million of building and leasehold improvements, $61.1 million and $47.4 million of right of use assets, $45.0 million and $42.2 million of accumulated depreciation, $114.7 million and $112.6 million of other assets included in other line items, $140.6 million and $140.8 million of real estate debt, net, $0.4 million and $0.4 million of accrued interest payable, $56.2 million and $43.6 million of lease liabilities, and $16.5 million and $18.3 million of other liabilities included in other line items as of March 31, 2019 and December 31, 2018, respectively.

Debt and Preferred Equity Inv_3

Debt and Preferred Equity Investments - Rollforward of Net Book Balance (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of period	$ 2,099,393	$ 2,114,041
Redemptions/Sales/Syndications/Amortization	(271,387)		$ (994,906)
Net change in loan loss reserves	4,000	(5,750)
Balance at end of period	2,272,241	$ 2,099,393	2,114,041
Debt Investments in Mortgage Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	436,819		834,304
Preferred equity investments
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Originations/Accretion	$ 3,416		$ 151,704

Debt and Preferred Equity Inv_4

Debt and Preferred Equity Investments - Rollforward of Total Allowance for Loan Loss Reserves (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Loan loss reserve activity
Balance at beginning of year	$ 5,750	$ 0
Expensed	0	6,839
Recoveries	0	0
Charge-offs and reclassifications	(4,000)	(1,089)
Balance at end of period	$ 1,750	$ 5,750

Debt and Preferred Equity Inv_5

Debt and Preferred Equity Investments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Aggregate weighted average current yield (as a percent)	8.79%
Debt Investments Held [Abstract]
Carrying Value	$ 2,272,241	$ 2,099,393
Mezzanine Loan, with an Initial Maturity Date of June 2024
Debt Investments Held [Abstract]
Amount participated out	12,000
Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Amount participated out	1,300
Debt Investments in Mortgage Loans
Debt Investments Held [Abstract]
Future Funding Obligations	143,096
Senior Financing	6,701,267
Carrying Value	2,034,620	1,812,936
Mezzanine Loan with an Initial Maturity Date of December 2018
Debt Investments Held [Abstract]
Amount participated out	14,600
Mezzanine Loan with an Initial Maturity Date of December 2018, 2
Debt Investments Held [Abstract]
Amount participated out	14,100
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	4,110,930
Carrying Value	624,132	430,099
Total fixed rate | Mezzanine Loan, September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000
Carrying Value	3,500	3,500
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
Carrying Value	24,937	24,932
Total fixed rate | Mezzanine Loan with an Initial Maturity of August 2022
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	280,000
Carrying Value	37,099	36,585
Total fixed rate | Mezzanine Loan With Maturity June 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	318,078
Carrying Value	202,184	0
Total fixed rate | Mezzanine Loan, November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	85,097
Carrying Value	12,708	12,706
Total fixed rate | Mezzanine Loan With An Initial Maturity Date Of December 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	180,000
Carrying Value	30,000	30,000
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
Carrying Value	12,943	12,941
Total fixed rate | Mezzanine Loan, January 2025
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	95,000
Carrying Value	30,000	30,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of June 2027
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,712,750
Carrying Value	55,250	55,250
Total fixed rate | Mezzanine Loan Sold In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	11,000
Total fixed rate | Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,163,005
Carrying Value	215,511	213,185
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	143,096
Senior Financing	2,590,337
Carrying Value	1,410,488	1,382,837
Total floating rate | Mezzanine Loan with an Initial Maturity Date of January 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	45,025
Carrying Value	37,500	37,499
Total floating rate | Mezzanine Loan with an Initial Maturity Date of April 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	150,000
Carrying Value	15,381	15,333
Total floating rate | Mezzanine Loan with an Initial Maturity Date of April 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	14,869	14,822
Total floating rate | Mezzanine Loan With An Initial Maturity Date Of April 2019, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	40,000
Carrying Value	19,999	19,986
Total floating rate | Mezzanine Loan With An Initial Maturity Date Of April 2019, 4
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	265,000
Carrying Value	24,993	24,961
Total floating rate | Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations	39,321
Senior Financing	236,424
Carrying Value	85,308	84,012
Total floating rate | Mortgage/Mezzanine Loan With An Initial Maturity Date Of August 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	19,999	19,999
Total floating rate | Mortgage/Mezzanine Loan with an Initial Maturity of September 2019
Debt Investments Held [Abstract]
Future Funding Obligations	1,027
Senior Financing	0
Carrying Value	128,560	154,070
Total floating rate | Mezzanine Loan with an Initial Maturity of October 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	350,000
Carrying Value	34,923	34,886
Total floating rate | Mortgage/Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations	9,656
Senior Financing	64,521
Carrying Value	112,886	62,493
Total floating rate | Mezzanine Loan with an Initial Maturity of January 2020
Debt Investments Held [Abstract]
Future Funding Obligations	509
Senior Financing	576,313
Carrying Value	94,118	79,164
Total floating rate | Mortgage/Mezzanine Loan Due March 2020 [Member]
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	69,310	0
Total floating rate | Mortgage Loan with an Initial Maturity of February 2020
Debt Investments Held [Abstract]
Future Funding Obligations	9,776
Senior Financing	0
Carrying Value	89,995	88,501
Total floating rate | Mezzanine Loan with an Initial Maturity Date of March 2020
Debt Investments Held [Abstract]
Future Funding Obligations	828
Senior Financing	324,989
Carrying Value	53,917	53,402
Total floating rate | Mortgage and Mezzanine Loan with an Initial Maturity Date of April 2020
Debt Investments Held [Abstract]
Future Funding Obligations	8,093
Senior Financing	0
Carrying Value	230,879	277,694
Total floating rate | Mortgage And Mezzanine Loan With An Initial Maturity Date Of June 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	62,957
Carrying Value	36,991	37,094
Total floating rate | Mezzanine Loan with an Initial Maturity of July 2020
Debt Investments Held [Abstract]
Future Funding Obligations	7,392
Senior Financing	39,649
Carrying Value	13,145	12,627
Total floating rate | Mortgage And Mezzanine Loan With An Initial Maturity Date Of October 2020
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	83,663	83,449
Total floating rate | Mezzanine Loan with an Initial Maturity of November 2020
Debt Investments Held [Abstract]
Future Funding Obligations	35,467
Senior Financing	375,459
Carrying Value	92,055	88,817
Total floating rate | Mortgage/Mezzanine Loan with an Initial Maturity of December 2020
Debt Investments Held [Abstract]
Future Funding Obligations	31,027
Senior Financing	0
Carrying Value	101,028	98,804
Total floating rate | Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	35,295	35,266
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
Carrying Value	15,674	15,665
Total floating rate | Mezzanine Loan Repaid In 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	7,305
Total floating rate | Mezzanine Loan Repaid In 2019, 2
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	14,998
Total floating rate | Mezzanine Loan Repaid In 2019, 3
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	$ 0	$ 21,990

Debt and Preferred Equity Inv_6

Debt and Preferred Equity Investments - Preferred Equity Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Preferred equity investment
Aggregate weighted average current yield (as a percent)	8.79%
Carrying Value	$ 2,272,241	$ 2,099,393
Preferred Equity, April 2021
Preferred equity investment
Future Funding Obligations	0
Senior Financing	272,000
Carrying Value	143,009	143,183
Preferred Equity, June 2022
Preferred equity investment
Future Funding Obligations	0
Senior Financing	1,762,761
Carrying Value	$ 94,612	143,274
Preferred equity investments
Preferred equity investment
Aggregate weighted average current yield (as a percent)	8.74%
Future Funding Obligations	$ 0
Senior Financing	2,034,761
Carrying Value	$ 237,621	$ 286,457

Debt and Preferred Equity Inv_7

Debt and Preferred Equity Investments - Narrative (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)loansegment	Dec. 31, 2018USD ($)segment	Dec. 31, 2017USD ($)
Preferred equity investment
Allowance for loan and lease losses, real estate	$ 1,750,000	$ 5,750,000	$ 0
Number of investments marketed for sale | loan	1
Impaired financing receivable, with related allowance, unpaid principal balance	$ 144,800,000
Number of portfolio segments of financial receivables (segment) | segment	1	1
Additional amount of financing receivables included in other assets	$ 89,600,000	$ 88,800,000
Recorded investment, nonaccrual status	$ 28,400,000
Weighted average risk rating		1.3
Mezzanine Loan
Preferred equity investment
Number of debt and equity investments not performing | loan	1
Financing Receivables, Equal to Greater than 90 Days Past Due
Preferred equity investment
Recorded investment, past due	$ 0	$ 0

Investments in Unconsolidated_3

Investments in Unconsolidated Joint Ventures - Additional Information (Details) $ in Thousands	May 08, 2019property	Feb. 28, 2019property	Oct. 31, 2016	Mar. 31, 2019USD ($)ft²unit	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
General information on each joint venture
Equity method investments				$ 3,055,368		$ 3,019,020
Net equity investment in VIEs in which the entity is not primary beneficiary				$ 869,500		808,300
Unaudited Approximate Square Feet (sqft) | ft²				30,028,056
Purchase price and other fair value adjustments				$ (2,041)	$ 49,293
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
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
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
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(5)
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
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
Number of properties sold | property		1
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
Maximum ownership percentage of partners				29.00%
Partners' ownership percentage				28.17%
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
2 Herald Square
General information on each joint venture
Ownership Interest				51.00%
Economic Interest (as a percent)				51.00%
Unaudited Approximate Square Feet (sqft) | ft²				369,000
Acquisition Price				$ 266,000
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
Joint venture
General information on each joint venture
Equity method investments				$ 3,055,368		$ 3,019,020
Equity method investments with negative book value				$ 79,700
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 | 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
Joint venture | 11 West 34th Street
General information on each joint venture
Economic Interest (as a percent)				30.00%
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 | 10 East 53rd Street
General information on each joint venture
Economic Interest (as a percent)				55.00%
Joint venture | 521 Fifth Avenue(5)
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 | 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 | 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%
Subsequent Event | Stonehenge Portfolio
General information on each joint venture
Number of properties sold | property	1

Investments in Unconsolidated_4

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
	Feb. 28, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Oct. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 3,055,368		$ 3,019,020
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate		17,166	$ (6,440)
Stonehenge Portfolio
Schedule of Equity Method Investments [Line Items]
Ownership Interest					90.00%
Mezzanine loan due February 2022
Schedule of Equity Method Investments [Line Items]
Equity method investments		44,824		44,357
Mezzanine Loans And Preferred Equity
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 44,824		$ 44,357
131-137 Spring Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest	20.00%
Gross Asset Valuation	$ 216,000
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	$ 17,660
103 East 86th Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest	1.00%
Gross Asset Valuation	$ 90,500
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	$ 19

Investments in Unconsolidated_5

Investments in Unconsolidated Joint Ventures - Mortgages and Other Loans Payable (Details)	May 08, 2019property	Feb. 28, 2019property	Mar. 31, 2019USD ($)extension	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Total fixed rate debt			$ 1,388,592,000	$ 1,389,717,000
Total floating rate debt			$ 658,314,000	598,442,000
1515 Broadway
Debt Instrument [Line Items]
Economic Interest (as a percent)			56.87%
Worldwide Plaza
Debt Instrument [Line Items]
Economic Interest (as a percent)			24.35%
Stonehenge Portfolio
Debt Instrument [Line Items]
Number of properties sold | property		1
2 Herald Square
Debt Instrument [Line Items]
Economic Interest (as a percent)			51.00%
Joint venture
Debt Instrument [Line Items]
Total fixed rate debt			$ 5,660,178,000	5,666,108,000
Total floating rate debt			3,211,761,000	3,387,705,000
Total fixed rate and floating rate debt			8,871,939,000	9,053,813,000
Deferred financing costs, net			(111,606,000)	(103,191,000)
Total joint venture mortgages and other loans payable, net			$ 8,760,333,000	8,950,622,000
Joint venture | 521 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			50.50%
Interest rate, fixed rate debt (as a percent)			3.73%
Total fixed rate debt			$ 170,000,000	170,000,000
Joint venture | 717 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			10.92%
Joint venture | 717 Fifth Avenue | Mortgage loan
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			4.45%
Total fixed rate debt			$ 300,000,000	300,000,000
Committed amount			$ 300,000,000
Joint venture | 717 Fifth Avenue | Mezzanine loans
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			5.50%
Total fixed rate debt			$ 355,328,000	355,328,000
Committed amount			$ 355,300,000
Joint venture | 650 Fifth Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			50.00%
Joint venture | 650 Fifth Avenue | Mortgage loan
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			4.46%
Total fixed rate debt			$ 210,000,000	210,000,000
Long-term debt, carrying value			$ 210,000,000
Joint venture | 650 Fifth Avenue | Mezzanine loans
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			5.45%
Total fixed rate debt			$ 65,000,000	65,000,000
Joint venture | 21 East 66th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			32.28%
Interest rate, fixed rate debt (as a percent)			3.60%
Interest rate, floating rate debt (as a percent)			2.75%
Total fixed rate debt			$ 12,000,000	12,000,000
Total floating rate debt			$ 1,552,000	1,571,000
Joint venture | 919 Third Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			51.00%
Interest rate, fixed rate debt (as a percent)			5.12%
Total fixed rate debt			$ 500,000,000	500,000,000
Joint venture | 1515 Broadway
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			3.93%
Total fixed rate debt			$ 851,492,000	855,876,000
Joint venture | 11 Madison Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			60.00%
Interest rate, fixed rate debt (as a percent)			3.84%
Total fixed rate debt			$ 1,400,000,000	1,400,000,000
Joint venture | 800 Third Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			60.52%
Interest rate, fixed rate debt (as a percent)			3.37%
Total fixed rate debt			$ 177,000,000	177,000,000
Joint venture | East 400 Street 57
Debt Instrument [Line Items]
Economic Interest (as a percent)			41.00%
Interest rate, fixed rate debt (as a percent)			3.00%
Total fixed rate debt			$ 99,311,000	99,828,000
Joint venture | Worldwide Plaza
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			3.98%
Total fixed rate debt			$ 1,200,000,000	1,200,000,000
Joint venture | Stonehenge Portfolio
Debt Instrument [Line Items]
Interest rate, fixed rate debt (as a percent)			4.20%
Total fixed rate debt			$ 320,047,000	321,076,000
Joint venture | 55 West 46th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			25.00%
Interest rate, floating rate debt (as a percent)			2.13%
Total floating rate debt			$ 188,939,000	185,569,000
Committed amount			195,000,000
Unused borrowing capacity, amount			$ 6,100,000
Joint venture | 1552 Broadway
Debt Instrument [Line Items]
Economic Interest (as a percent)			50.00%
Interest rate, floating rate debt (as a percent)			2.65%
Total floating rate debt			$ 195,000,000	195,000,000
Joint venture | 280 Park Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			50.00%
Interest rate, floating rate debt (as a percent)			1.73%
Total floating rate debt			$ 1,200,000,000	1,200,000,000
Joint venture | 121 Greene Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			50.00%
Interest rate, floating rate debt (as a percent)			1.50%
Total floating rate debt			$ 15,000,000	15,000,000
Joint venture | 10 East 53rd Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			55.00%
Interest rate, floating rate debt (as a percent)			2.25%
Total floating rate debt			$ 170,000,000	170,000,000
Joint venture | 11 West 34th Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			30.00%
Interest rate, floating rate debt (as a percent)			1.45%
Total floating rate debt			$ 23,000,000	23,000,000
Joint venture | 100 Park Avenue
Debt Instrument [Line Items]
Economic Interest (as a percent)			49.90%
Interest rate, floating rate debt (as a percent)			1.75%
Total floating rate debt			$ 359,705,000	360,000,000
Joint venture | One Vanderbilt
Debt Instrument [Line Items]
Economic Interest (as a percent)			71.01%
Interest rate, floating rate debt (as a percent)			2.75%
Total floating rate debt			$ 375,000,000	375,000,000
Joint venture | One Vanderbilt | Construction Loans
Debt Instrument [Line Items]
Maximum facility capacity			$ 1,750,000,000
Term (in Years)			5 years
Number of extension options | extension			2
Period of extension options			1 year
Joint venture | 2 Herald Square
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)			1.55%
Total floating rate debt			$ 133,565,000	133,565,000
Committed amount			$ 150,000,000
Joint venture | 605 West 42nd Street
Debt Instrument [Line Items]
Economic Interest (as a percent)			20.00%
Interest rate, floating rate debt (as a percent)			1.44%
Total floating rate debt			$ 550,000,000	550,000,000
Joint venture | 131-137 Spring Street
Debt Instrument [Line Items]
Total floating rate debt			0	141,000,000
Joint venture | 103 East 86th Street
Debt Instrument [Line Items]
Total floating rate debt			0	$ 38,000,000
Mezzanine Loan, Initial Maturity October 2022 | Joint venture | 650 Fifth Avenue | Mezzanine loans
Debt Instrument [Line Items]
Long-term debt, carrying value			65,000,000
Secured Debt, Initial Maturity August 2019 | Joint venture | Stonehenge Portfolio
Debt Instrument [Line Items]
Total fixed rate debt			133,600,000
Secured Debt, Initial Maturity June 2024 | Joint venture | Stonehenge Portfolio
Debt Instrument [Line Items]
Total fixed rate debt			53,800,000
Secured Debt, Initial Maturity April 2028 | Joint venture | Stonehenge Portfolio
Debt Instrument [Line Items]
Total fixed rate debt			$ 132,600,000
Subsequent Event | Stonehenge Portfolio
Debt Instrument [Line Items]
Number of properties sold | property	1

Investments in Unconsolidated_6

Investments in Unconsolidated Joint Ventures - Schedules of Combined Financial Statements for the Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets
Commercial real estate property, net	$ 6,782,418		$ 6,414,798
Cash and cash equivalents	144,323	$ 288,808	129,475
Tenant and other receivables, related party receivables, and deferred rents receivable	47,829		41,589
Other assets	324,629		295,679
Liabilities and equity
Mortgages and other loans payable, net	2,018,561		1,961,240
Deferred revenue/gain	102,598		94,453
Lease liabilities	389,857		3,603
Other liabilities	135,448		116,566
Company's investments in unconsolidated joint ventures	3,055,368		3,019,020
Combined statements of income for the unconsolidated joint ventures
Operating expenses	57,698	59,782
Real estate taxes	46,688	45,661
Interest expense, net of interest income	50,525	47,916
Amortization of deferred financing costs	2,742	3,537
Transaction related costs	55	162
Depreciation and amortization	68,343	69,388
Total expenses	260,328	258,282
Company's equity in net (loss) income from unconsolidated joint ventures (1)	(5,234)	4,036
Joint venture
Assets
Commercial real estate property, net	14,362,952		14,347,673
Cash and cash equivalents	370,832		381,301
Tenant and other receivables, related party receivables, and deferred rents receivable	321,696		273,141
Debt and preferred equity investments, net	44,824		44,357
Other assets	2,191,441		2,187,166
Total assets	17,291,745		17,233,638
Liabilities and equity
Mortgages and other loans payable, net	8,760,333		8,950,622
Deferred revenue/gain	1,620,437		1,660,838
Lease liabilities	901,808		637,168
Other liabilities	341,134		309,145
Equity	5,668,033		5,675,865
Total liabilities and equity	17,291,745		17,233,638
Company's investments in unconsolidated joint ventures	3,055,368		$ 3,019,020
Combined statements of income for the unconsolidated joint ventures
Total revenues	307,519	320,941
Operating expenses	54,124	59,773
Operating lease rent	5,901	4,393
Real estate taxes	54,236	57,027
Interest expense, net of interest income	96,623	89,741
Amortization of deferred financing costs	5,216	5,116
Depreciation and amortization	104,331	105,080
Total expenses	320,431	321,130
Net loss before gain on sale (1)	(12,912)	(189)
Company's equity in net (loss) income from unconsolidated joint ventures (1)	(5,234)	4,036
Management Service, Base | Joint venture
Investment in Unconsolidated Joint Ventures
Escalation and reimbursement	$ 2,500	$ 3,800

Deferred Costs (Details)

Deferred Costs (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred leasing costs	$ 463,521	$ 453,833
Less: accumulated amortization	(251,906)	(244,723)
Deferred costs, net	$ 211,615	$ 209,110

Mortgages and Other Loans Pay_3

Mortgages and Other Loans Payable (Details)	3 Months Ended
	Mar. 31, 2019USD ($)extension	Dec. 31, 2018USD ($)	Apr. 30, 2018USD ($)
Debt Instrument [Line Items]
Total fixed rate debt	$ 1,388,592,000	$ 1,389,717,000
Total floating rate debt	658,314,000	598,442,000
Total mortgages and other loans payable	2,046,906,000	1,988,159,000
Deferred financing costs, net of amortization	(28,345,000)	(26,919,000)
Total mortgages and other loans payable, net	2,018,561,000	1,961,240,000
Book value of collateral	4,100,000,000	3,900,000,000
Outstanding under line of credit facility	782,656,000	492,196,000
FHLB Facility
Debt Instrument [Line Items]
Total floating rate debt	$ 13,000,000	13,000,000
FHLB Facility | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	0.27%
Uncommitted Master Repurchase Agreement 2017
Debt Instrument [Line Items]
Total floating rate debt	$ 300,000,000	300,000,000
Term (in Years)	1 year
Maximum facility capacity	$ 300,000,000		$ 400,000,000
Number of extension options | extension	2
Period of extension options	1 year
Extension option exercised, term	1 year
Outstanding under line of credit facility	$ 299,900,000
Uncommitted Master Repurchase Agreement 2017 | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.34%
FHLB Facility, December 2019
Debt Instrument [Line Items]
Total floating rate debt	$ 14,500,000	14,500,000
FHLB Facility, December 2019 | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	0.18%
FHLB Facility, January 2020
Debt Instrument [Line Items]
Total floating rate debt	$ 10,000,000	0
FHLB Facility, January 2020 | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	0.26%
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	$ 212,463,000	213,208,000
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	$ 39,724,000	39,931,000
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	$ 35,634,000	35,807,000
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%
113 Greene Street
Debt Instrument [Line Items]
Total floating rate debt	$ 15,523,000	15,523,000
113 Greene Street | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.00%
609 Fifth Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 49,872,000	0
609 Fifth Avenue | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.40%
185 Broadway
Debt Instrument [Line Items]
Total floating rate debt	$ 111,869,000	111,869,000
185 Broadway | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.85%
712 Madison Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 28,000,000	28,000,000
712 Madison Avenue | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	2.50%
115 Spring Street
Debt Instrument [Line Items]
Total floating rate debt	$ 65,550,000	65,550,000
115 Spring Street | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	3.40%
719 Seventh Avenue
Debt Instrument [Line Items]
Total floating rate debt	$ 50,000,000	$ 50,000,000
719 Seventh Avenue | Weighted Average
Debt Instrument [Line Items]
Interest rate, floating rate debt (as a percent)	1.20%
Construction Loans | 185 Broadway
Debt Instrument [Line Items]
Term (in Years)	3 years
Maximum facility capacity	$ 225,000,000
Number of extension options | extension	2
Period of extension options	1 year
LIBOR Plus 27 Basis Points | Ticonderoga Insurance Company
Debt Instrument [Line Items]
FHLB advances	$ 13,000,000
LIBOR Plus 27 Basis Points | Ticonderoga Insurance Company | LIBOR
Debt Instrument [Line Items]
Interest rate added to base rate (as a percent)	0.27%
LIBOR Plus 18 Basis Points | Ticonderoga Insurance Company
Debt Instrument [Line Items]
FHLB advances	$ 14,500,000
LIBOR Plus 18 Basis Points | Ticonderoga Insurance Company | LIBOR
Debt Instrument [Line Items]
Interest rate added to base rate (as a percent)	0.18%
LIBOR Plus 26 Basis Points | Ticonderoga Insurance Company
Debt Instrument [Line Items]
FHLB advances	$ 10,000,000
LIBOR Plus 26 Basis Points | Ticonderoga Insurance Company | LIBOR
Debt Instrument [Line Items]
Interest rate added to base rate (as a percent)	0.26%

Corporate Indebtedness - Additi

Corporate Indebtedness - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019USD ($)extension	Dec. 31, 2018USD ($)
Corporate Indebtedness
Outstanding under line of credit facility	$ 782,656,000	$ 492,196,000
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	$ 790,000,000
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	700,000,000
2012 Credit Facility | Line of Credit
Corporate Indebtedness
Long-term debt, carrying value	782,700,000	$ 492,200,000
Term Loan A, Maturity March 31, 2023 | Term loan
Corporate Indebtedness
Credit facility, maximum borrowing capacity	$ 1,300,000,000
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
Number of extensions | extension	2
Term of extension	6 months
Maximum borrowing capacity, optional expansion	$ 4,500,000,000
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

Corporate Indebtedness - Senior Unsecured Notes (Details) - USD ($)	1 Months Ended	3 Months Ended
	Oct. 31, 2017	Mar. 31, 2019	Dec. 31, 2018
Debt disclosures by scheduled maturity date
Accreted Balance		$ 1,493,357,000	$ 1,493,051,000
Senior unsecured notes
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		1,500,000,000
Accreted Balance		1,503,534,000	1,503,759,000
Deferred financing costs, net		(8,044,000)	(8,545,000)
Accreted Balance, net of deferred financing costs		1,495,490,000	1,495,214,000
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 | Senior Unsecured Notes Due August 2021
Debt disclosures by scheduled maturity date
Unpaid Principal Balance		$ 350,000,000
Accreted Balance		$ 350,000,000	350,000,000
Coupon Rate (as a percent)		0.98%
Initial Term (in Years)		3 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		$ 499,616,000	499,591,000
Coupon Rate (as a percent)		3.25%
Initial Term (in Years)		5 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		$ 303,918,000	304,168,000
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 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
Redemption price, percentage	105.334%

Corporate Indebtedness - Junior

Corporate Indebtedness - Junior Subordinated Deferrable Interest Debentures and Principal Maturities (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2005	Mar. 31, 2019
Principal Repayments and Joint Venture Debt
Remaining 2019		$ 32,643,000
2020		586,641,000
2021		551,379,000
2022		1,007,985,000
2023		2,212,851,000
Thereafter		1,545,407,000
Total principal repayments		$ 5,936,906,000
Trust Preferred Securities
Debt Instrument [Line Items]
Proceeds from issuance of debt	$ 100,000,000
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 2019		$ 112,359,000
2020		251,433,000
2021		522,359,000
2022		220,810,000
2023		277,996,000
Thereafter		2,430,198,000
Total principal repayments		3,815,155,000
Joint venture | Trust Preferred Securities
Principal Repayments and Joint Venture Debt
Remaining 2019		0
2020		0
2021		0
2022		0
2023		0
Thereafter		100,000,000
Total principal repayments		100,000,000
Joint venture | Mortgages and other loans payable
Scheduled Amortization
Remaining 2019		5,143,000
2020		11,118,000
2021		11,638,000
2022		9,430,000
2023		7,301,000
Thereafter		9,291,000
Total amortization of debt		53,921,000
Principal Repayments and Joint Venture Debt
Remaining 2019		27,500,000
2020		325,523,000
2021		189,741,000
2022		198,555,000
2023		115,550,000
Thereafter		1,136,116,000
Total principal repayments		1,992,985,000
Joint venture | Revolving Credit Facility
Principal Repayments and Joint Venture Debt
Remaining 2019		0
2020		0
2021		0
2022		0
2023		790,000,000
Thereafter		0
Total principal repayments		790,000,000
Joint venture | Unsecured Term Loans
Principal Repayments and Joint Venture Debt
Remaining 2019		0
2020		0
2021		0
2022		0
2023		1,300,000,000
Thereafter		200,000,000
Total principal repayments		1,500,000,000
Joint venture | Senior Unsecured Notes
Principal Repayments and Joint Venture Debt
Remaining 2019		0
2020		250,000,000
2021		350,000,000
2022		800,000,000
2023		0
Thereafter		100,000,000
Total principal repayments		$ 1,500,000,000

Corporate Indebtedness - Schedu

Corporate Indebtedness - Schedule of Consolidated Interest Expense, Excluding Capitalized Interest (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Interest expense
Interest expense before capitalized interest	$ 60,810	$ 54,132
Interest on financing leases	804	786
Interest capitalized	(10,509)	(6,686)
Interest income	(580)	(316)
Interest expense, net	$ 50,525	$ 47,916

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Amounts due from/to related parties
Due from joint ventures		$ 20,723		$ 18,655
Other		8,735		9,378
Related party receivables		29,458		$ 28,033
Alliance Building Services
Related Party Transactions
Profit participation from related party		900	$ 1,000
Payments made for services		2,900	4,000
Entity with Stephen L Green ownership interest
Related Party Transactions
Property management fees from related party		100	$ 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 t_3

Noncontrolling Interests on the Company's Consolidated Financial Statements - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)shares$ / shares	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period | $	$ 387,805
Net income | $	2,278	$ 5,272
Accumulated other comprehensive income allocation | $	(1,003)	619
Balance at end of period | $	$ 412,361		$ 387,805
Number of company common stock issued on conversion of Series B preferred units	6.71348
Series B Preferred Unit
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Preferred units, issued (in shares) | shares	0
SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	4.87%		4.70%
Number of units of operating partnership owned by the noncontrolling interest unit holders (shares) | shares	4,260,685		4,130,579
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) | shares	4,260,685
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period | $	$ 387,805	461,954	$ 461,954
Distributions | $	(3,643)			$ (15,000)
Issuance of common units | $	14,135			23,655
Redemption of common units | $	(16,143)			(60,718)
Net income | $	2,278			12,216
Accumulated other comprehensive income allocation | $	(1,003)	$ 619		(66)
Fair value adjustment | $	28,932			(34,236)
Balance at end of period | $	$ 412,361		$ 387,805	$ 461,954
SL Green Operating Partnership | 4.50% Series G
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	4.50%
Preferred units, shares authorized (in shares) | shares	1,902,000
Number of preferred units issued (in shares) | shares	1,902,000
Annual dividends on preferred units (in dollars per share)	$ 1.1250
Liquidation preference of preferred units (in dollars per share)	25
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 | 7.00% Series F
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	7.00%
Preferred units, shares authorized (in shares) | shares	60
Number of preferred units issued (in shares) | shares	60
Annual dividends on preferred units (in dollars per share)	$ 70
Liquidation preference of preferred units (in dollars per share)	1,000
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 29.12
SL Green Operating Partnership | 3.50% Series K
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.50%
Preferred units, shares authorized (in shares) | shares	700,000
Number of preferred units issued (in shares) | shares	563,954
Annual dividends on preferred units (in dollars per share)	$ 0.8750
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 134.67
SL Green Operating Partnership | 4.00% Series L
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	4.00%
Preferred units, shares authorized (in shares) | shares	500,000
Number of preferred units issued (in shares) | shares	378,634
Annual dividends on preferred units (in dollars per share)	$ 1
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 3.75% Series M
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.75%
Preferred units, shares authorized (in shares) | shares	1,600,000
Number of preferred units issued (in shares) | shares	1,600,000
Annual dividends on preferred units (in dollars per share)	$ 0.9375
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 3.00% Series N
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.00%
Preferred units, shares authorized (in shares) | shares	552,303
Number of preferred units issued (in shares) | shares	552,303
Annual dividends on preferred units (in dollars per share)	$ 0.7500
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | Series O
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Preferred units, shares authorized (in shares) | shares	1
Number of preferred units issued (in shares) | shares	1
Annual dividends on preferred units (in dollars per share)	$ (6)
Liquidation preference of preferred units (in dollars per share)	(6)
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 4.00% Series P
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	4.00%
Preferred units, shares authorized (in shares) | shares	200,000
Number of preferred units issued (in shares) | shares	200,000
Annual dividends on preferred units (in dollars per share)	$ 1
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 3.50% Series Q
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.50%
Preferred units, shares authorized (in shares) | shares	268,000
Number of preferred units issued (in shares) | shares	268,000
Annual dividends on preferred units (in dollars per share)	$ 0.8750
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 148.95
SL Green Operating Partnership | 3.50% Series R
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.50%
Preferred units, shares authorized (in shares) | shares	400,000
Number of preferred units issued (in shares) | shares	400,000
Annual dividends on preferred units (in dollars per share)	$ 0.8750
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 154.89
SL Green Operating Partnership | 4.00% Series S
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	4.00%
Preferred units, shares authorized (in shares) | shares	1,077,280
Number of preferred units issued (in shares) | shares	1,077,280
Annual dividends on preferred units (in dollars per share)	$ 1
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 2.75% Series T
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	2.75%
Preferred units, shares authorized (in shares) | shares	230,000
Number of preferred units issued (in shares) | shares	230,000
Annual dividends on preferred units (in dollars per share)	$ 0.6875
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 119.02
SL Green Operating Partnership | 4.50% Series U
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	4.50%
Preferred units, shares authorized (in shares) | shares	680,000
Number of preferred units issued (in shares) | shares	680,000
Annual dividends on preferred units (in dollars per share)	$ 1.1250
Liquidation preference of preferred units (in dollars per share)	25
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 3.50% Series A
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	3.50%
Preferred units, shares authorized (in shares) | shares	109,161
Number of preferred units issued (in shares) | shares	109,161
Annual dividends on preferred units (in dollars per share)	$ 35
Liquidation preference of preferred units (in dollars per share)	1,000
Operating partnership common stock value use for conversion of preferred units (in dollars per share)	$ 0
SL Green Operating Partnership | 3.50% Series A | Minimum
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Dividend rate preferred units (as a percent)	75.00%

Noncontrolling Interests on t_4

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Rollforward Analysis of Preferred Unit Activity
Issuance of preferred units	$ 14,135		$ 23,655
Redemption of preferred units	(16,143)		(60,718)
Preferred Units
Rollforward Analysis of Preferred Unit Activity
Balance at beginning of period	300,427	$ 301,735
Issuance of preferred units	0	0
Redemption of preferred units	(15,142)	(1,308)
Balance at end of period	$ 285,285	$ 300,427	$ 301,735

Stockholders' Equity of the C_3

Stockholders' Equity of the Company - Additional Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019USD ($)increase$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Jun. 30, 2018USD ($)	Aug. 31, 2016USD ($)
Equity, Class of Treasury Stock [Line Items]
Authorized capital stock (shares)	260,000,000
Authorized shares, par value (in dollars per share) | $ / shares	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	160,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Excess stock, shares authorized (shares)	75,000,000
Excess stock, par value (in dollars per share) | $ / shares	$ 0.01
Preferred stock, shares authorized (shares)	25,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Excess shares issued (shares)	0
Shares repurchased	397,783	9,744,911	8,342,411
Average price paid per share (in dollars per share) | $ / shares	$ 86.07	$ 96.22	$ 101.64
2016 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount | $		$ 500,000,000	$ 500,000,000	$ 500,000,000	$ 1,000,000,000
Number of increases to share repurchase program | increase	3
Shares repurchased	18,485,105	18,087,322	8,342,411
Stock repurchase program, authorized amount | $	$ 2,500,000,000

Stockholders' Equity of the C_4

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, 2019	Dec. 31, 2018	Feb. 28, 2018
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	$ 25
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 C_5

Stockholders' Equity of the Company - Schedule of Common Stock Issued and Proceeds Received Dividend Reinvestments (Details) - Dividend Reinvestment and Stock Purchase Plan (DRIP) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stockholders' Equity
Issuance of common stock (in shares)	540	447
Dividend reinvestments/stock purchases under the DRSPP	$ 47	$ 42

Stockholders' Equity of the C_6

Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic Earnings:
Income attributable to SL Green common stockholders	$ 43,792	$ 101,766
Net Income (Loss) Available To Common Stockholders, After Distributed And Undistributed Earnings Allocation, Basic	43,668	101,615
Effect of Dilutive Securities:
Add back: distributed earnings allocated to participating securities	124	109
Add back: undistributed earnings allocated to participating securities	0	42
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 46,070	$ 107,038
Basic Shares:
Weighted average common shares outstanding (shares)	83,313,000	90,520,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	4,333,000	4,683,000
Stock-based compensation plans (shares)	164,000	53,000
Diluted weighted average common stock outstanding (shares)	87,810,000	95,256,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,211,943
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 2,278	$ 5,272

Partners' Capital of the Oper_3

Partners' Capital of the Operating Partnership - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019shares	Dec. 31, 2018shares	Jun. 30, 2018shares	Mar. 31, 2018shares	Dec. 31, 2017shares
Common Stock
Stockholders' Equity
Units outstanding (units)		83,684,000	83,272,000	89,135,000	92,803,000
SL Green Operating Partnership
Stockholders' Equity
Noncontrolling interest in the operating partnership (as a percent)	4.87%	4.70%
Number of units of operating partnership owned by the noncontrolling interest unit holders (units)	4,260,685	4,130,579
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)	83,272,202

Partners' Capital of the Oper_4

Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator
Net Income (Loss) Available To Common Stockholders, After Distributed And Undistributed Earnings Allocation, Basic	$ 43,668	$ 101,615
Add back: distributed earnings allocated to participating securities	124	109
Add back: undistributed earnings allocated to participating securities	0	42
Income attributable to SL Green common stockholders	$ 46,070	$ 107,038
Denominator
Weighted average common shares outstanding (shares)	83,313,000	90,520,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,211,943
SL Green Operating Partnership
Numerator
Net income attributable to SLGOP common unitholders	$ 46,070	$ 107,038
Less: distributed earnings allocated to participating securities	(124)	(109)
Less: undistributed earnings allocated to participating securities	0	(42)
Net Income (Loss) Available To Common Stockholders, After Distributed And Undistributed Earnings Allocation, Basic	45,946	106,887
Add back: distributed earnings allocated to participating securities	124	109
Add back: undistributed earnings allocated to participating securities	0	42
Income attributable to SL Green common stockholders	$ 46,070	$ 107,038
Denominator
Weighted average common shares outstanding (shares)	87,646,000	95,203,000
Stock-based compensation plans (shares)	164,000	53,000
Diluted weighted average common units outstanding (shares)	87,810,000	95,256,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,211,943	1,210,802

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Details) $ / shares in Units, fungible_unit in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)unit / sharesunitfungible_unit$ / sharesshares	Mar. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Aug. 31, 2014	Jan. 01, 2008shares
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	$ 500,000	$ 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 2 months
Remaining average contractual life of the options exercisable (in years)	3 years 2 months
Total unrecognized compensation cost related to unvested stock awards	$ 1,900,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)	9 months
Weighted average fair value of options granted during the period	$ 0		$ 84,068
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
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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	$ 3,411,841	12,757,704
Total unrecognized compensation cost related to unvested stock awards	$ 19,400,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)	2 years 1 month
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	$ 11,800,000			$ 9,800,000
Weighted average fair value of options granted during the period	$ 474,480	$ 13,440,503
Awards granted (in shares) | shares	6,000	162,900
Awards outstanding (in shares) | shares	3,452,066		3,452,016	3,298,216
LTIP units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of options granted during the period	$ 41,600,000			$ 22,000,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested stock awards	$ 28,500,000
Weighted average period for recognition of compensation cost related to unvested stock awards (in years)	2 years 8 months
Share-based compensation	$ 8,000,000	$ 6,900,000
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	4.5
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	$ 600,000	1,600,000
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
Award expiration period (in years)	10 years
2014 Outperformance Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 0
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
Deferred Stock Compensation Plan for Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$ 1,900,000	$ 2,200,000
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	14,298
Shares issued (in shares) | shares	9,722
Awards outstanding (in shares) | shares	124,576
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	120,085

Share-based Compensation - Stoc

Share-based Compensation - Stock Options and Restricted Stock Activity (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	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)	0.00%			2.85%
Expected life of option (in years)	0 years			3 years 5 months 24 days
Risk-free interest rate (as a percent)	0.00%			2.48%
Expected stock price volatility (as a percent)	0.00%			22.00%
Options Outstanding
Balance at beginning of period (in shares)	1,137,017	1,548,719	1,548,719
Granted (in shares)	0		6,000
Exercised (in shares)	0		(316,302)
Lapsed or cancelled (in shares)	(5,999)		(101,400)
Balance at end of period (in shares)	1,131,018		1,137,017	1,548,719
Options exercisable at end of period (in shares)	994,045		783,035
Total fair value of options granted during the period	$ 0		$ 84,068
Weighted Average Exercise Price
Balance at beginning of year (in dollars per share)	$ 103.54	$ 101.48	$ 101.48
Granted (in dollars per share)	0		97.91
Exercised (in dollars per share)	0		90.22
Lapsed or cancelled (in dollars per share)	110.56		113.22
Balance at end of period (in dollars per share)	103.50		103.54	$ 101.48
Options exercisable at end of period (in dollars per share)	$ 103		$ 101.28
Restricted Stock Awards
Options Outstanding
Total fair value of options granted during the period	$ 474,480	$ 13,440,503
Summary of restricted stock
Balance at beginning of year (in shares)	3,452,016	3,298,216	3,298,216
Granted (in shares)	6,000	162,900
Cancelled (in shares)	(5,950)	(9,100)
Balance at end of period (in shares)	3,452,066		3,452,016	3,298,216
Vested during the period (in shares)	110,274	92,114

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	$ 5,947,855
Other comprehensive (loss) income before reclassifications	(18,105)
Amounts reclassified from accumulated other comprehensive income	(1,008)
Ending Balance	5,844,323
Deferred net losses from terminated hedges	800	$ 1,300
Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	9,716
Other comprehensive (loss) income before reclassifications	(11,864)
Amounts reclassified from accumulated other comprehensive income	(530)
Ending Balance	(2,678)
Net unrealized gain on marketable securities
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	1,093
Other comprehensive (loss) income before reclassifications	731
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	1,824
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	15,108
Ending Balance	(4,005)
Joint venture | Net unrealized (loss) gain on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
Beginning Balance	4,299
Other comprehensive (loss) income before reclassifications	(6,972)
Amounts reclassified from accumulated other comprehensive income	(478)
Ending Balance	$ (3,151)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair Value of Financial Instruments
Marketable securities	$ 29,406		$ 28,638
Interest rate cap and swap agreements (included in other assets)	13,644		18,676
Purchase price and other fair value adjustments	(2,041)	$ 49,293
Debt and preferred equity investments	2,272,241		2,099,393
Equity method investments	3,055,368		3,019,020
Additional amount of financing receivables included in other assets	89,600		88,800
Carrying Value
Fair Value of Financial Instruments
Debt and preferred equity investments	2,272,241		2,099,393
Fixed rate debt	3,542,126		3,543,476
Variable rate debt	2,398,314		2,048,442
Total	5,940,440		5,591,918
Fair Value
Fair Value of Financial Instruments
Marketable securities	29,406		28,638
Total	6,031,768		5,288,093
Estimated fair value of debt and preferred equity investments, low end of range	2,300,000		2,100,000
Estimated fair value of debt and preferred equity investments, high end of range	2,500,000		2,300,000
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)	13,644		18,676
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	3,627,127		3,230,127
Variable rate debt	2,404,641		2,057,966
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	29,406		28,638
Commercial mortgage-backed securities | Level 2
Fair Value of Financial Instruments
Marketable securities	29,406		28,638
Joint venture
Fair Value of Financial Instruments
Equity method investments	3,055,368		3,019,020
919 Third Avenue | Joint venture | 919 Third Avenue
Fair Value of Financial Instruments
Purchase price and other fair value adjustments	49,300
Accrued Interest Payable And Other
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other liabilities)	15,644		7,663
Accrued Interest Payable And Other | Level 1
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other liabilities)	0		0
Accrued Interest Payable And Other | Level 2
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other liabilities)	15,644		7,663
Accrued Interest Payable And Other | Level 3
Fair Value of Financial Instruments
Interest rate cap and swap agreements (included in other liabilities)	$ 0		$ 0

Financial Instruments_ Deriva_3

Financial Instruments: Derivatives and Hedging (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Financial Instruments: Derivatives and Hedging
Fair Value	$ 13,644		$ 18,676
Gain (loss) from changes in fair value	(100)	$ (200)
Fair value of derivatives in a net liability position	15,700
Aggregate termination value	16,200
Estimated current balance held in accumulated other comprehensive loss to be reclassified into earnings within the next 12 months	900
Share of joint venture of accumulated other comprehensive loss reclassified into equity in net income from unconsolidated joint ventures within the next 12 months	400
Amount of Gain (Loss) Recognized in Other Comprehensive Loss	(17,332)	10,595
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	903	(428)
Interest Rate Cap Expiring September 2019
Financial Instruments: Derivatives and Hedging
Notional Value	$ 137,500
Strike Rate	4.00%
Fair Value	$ 0
Interest Rate Cap Expiring December 2019
Financial Instruments: Derivatives and Hedging
Notional Value	$ 111,869
Strike Rate	3.50%
Fair Value	$ 0
Interest Rate Swap Expiring November 2020
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000
Strike Rate	1.928%
Fair Value	$ 574
Interest Rate Swap Expiring November 2020, 2
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000
Strike Rate	1.934%
Fair Value	$ 565
Interest Rate Cap Expiring March 2021
Financial Instruments: Derivatives and Hedging
Notional Value	$ 85,000
Strike Rate	4.00%
Fair Value	$ 1
Interest Rate Swap Expiring in July 2023
Financial Instruments: Derivatives and Hedging
Notional Value	$ 200,000
Strike Rate	1.131%
Fair Value	$ 8,418
Interest Rate Swap Expiring in July 2023, 2
Financial Instruments: Derivatives and Hedging
Notional Value	$ 100,000
Strike Rate	1.161%
Fair Value	$ 4,086
Interest Rate Swap Expiring January 2024
Financial Instruments: Derivatives and Hedging
Notional Value	$ 150,000
Strike Rate	2.6955%
Fair Value	$ (3,688)
Interest Rate Swap Expiring January 2026
Financial Instruments: Derivatives and Hedging
Notional Value	$ 150,000
Strike Rate	2.721%
Fair Value	$ (5,078)
Interest Rate Swap Expiring January 2026, 2
Financial Instruments: Derivatives and Hedging
Notional Value	$ 200,000
Strike Rate	2.74%
Fair Value	$ (6,878)
Interest Rate Swaps/Caps
Financial Instruments: Derivatives and Hedging
Amount of Gain (Loss) Recognized in Other Comprehensive Loss	(11,963)	7,282
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	535	(338)
Interest Rate Contract
Financial Instruments: Derivatives and Hedging
Fair Value	(2,000)
Joint venture
Financial Instruments: Derivatives and Hedging
Amount of Gain (Loss) Recognized in Other Comprehensive Loss	(5,369)	3,313
Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion)	$ 368	$ (90)

Rental Income - Future Minimum

Rental Income - Future Minimum Rents (Details) $ in Thousands	Mar. 31, 2019USD ($)
Lessor, Lease, Description [Line Items]
Total payments to be received	$ 1,800,000
Consolidated properties
Lessor, Lease, Description [Line Items]
Remaining 2019	638,682
2020	801,572
2021	654,113
2022	591,562
2023	527,679
2024	487,263
Thereafter	3,068,298
Total payments to be received	6,769,169
Unconsolidated properties
Lessor, Lease, Description [Line Items]
Remaining 2019	265,578
2020	385,998
2021	392,375
2022	373,353
2023	344,592
2024	315,338
Thereafter	1,854,001
Total payments to be received	$ 3,931,235

Rental Income - Future Minimu_2

Rental Income - Future Minimum Rental Payments prior to Adoption (Details) $ in Thousands	Dec. 31, 2018USD ($)
Consolidated properties
Property Subject to or Available for Operating Lease [Line Items]
2019	$ 830,336
2020	765,610
2021	625,956
2022	562,250
2023	500,499
Thereafter	3,272,014
Total future minimum payments receivable	6,556,665
Unconsolidated properties
Property Subject to or Available for Operating Lease [Line Items]
2019	348,060
2020	375,228
2021	380,886
2022	348,222
2023	333,501
Thereafter	2,098,995
Total future minimum payments receivable	$ 3,884,892

Rental Income - Lease Income (D

Rental Income - Lease Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Fixed lease payments	$ 211,430	$ 213,007
Variable lease payments	27,479	26,399
Total lease payments	238,909	239,406
Amortization of acquired above and below-market leases	1,209	2,362
Total rental revenue	$ 240,118	$ 241,768

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Finance lease, cost	$ 1,100
Interest on financing leases	804	$ 786
Finance lease, right-of-use asset, amortization	300
Operating lease rent	$ 8,298	$ 8,308
Operating lease, weighted average discount rate, percent	8.44%
Operating lease, weighted average remaining lease term	67 years
Financing leases
Remaining 2019	$ 1,814
2020	2,619
2021	2,794
2022	2,794
2023	2,794
2024	2,819
Thereafter	814,283
Total minimum lease payments	829,917
Amount representing interest	786,094
Lease liabilities	43,823		$ 43,616
Operating leases (1)
Remaining 2019	23,303
2020	31,437
2021	31,629
2022	29,472
2023	27,166
2024	27,183
Thereafter	648,905
Total minimum lease payments	819,095
Amount discounted using incremental borrowing rate	(429,238)
Lease liabilities	389,857		$ 3,603
Total minimum sublease rentals to be received	$ 1,800,000
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract	3 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, term of contract	95 years

Segment Information - Additiona

Segment Information - Additional Information (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2019USD ($)segment	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Segment information
Number of reportable segments (segment) | segment		2
Total revenues		$ 304,255	$ 301,695
Net income		52,769	113,823
Total assets	[1]	13,385,774		$ 12,751,358
Marketing, general and administrative		25,979	23,528
Operating Segments | Real Estate Segment
Segment information
Total revenues		254,224	256,405
Net income		21,572	80,035
Total assets		10,943,516		10,481,594
Operating Segments | Debt and Preferred Equity Segment
Segment information
Total revenues		50,031	45,290
Net income		31,197	$ 33,788
Total assets		$ 2,442,258		$ 2,269,764
[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: $110.0 million and $110.0 million of land, $0.3 billion and $0.3 billion of building and improvements, $0.0 million and $2.0 million of building and leasehold improvements, $61.1 million and $47.4 million of right of use assets, $45.0 million and $42.2 million of accumulated depreciation, $114.7 million and $112.6 million of other assets included in other line items, $140.6 million and $140.8 million of real estate debt, net, $0.4 million and $0.4 million of accrued interest payable, $56.2 million and $43.6 million of lease liabilities, and $16.5 million and $18.3 million of other liabilities included in other line items as of March 31, 2019 and December 31, 2018, respectively.

Segment Information - Schedule

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, 2019	Mar. 31, 2018
Reconciliation of income from continuing operations to net income attributable to SL Green common stockholders
Net income before equity in net gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, (loss) gain on sale of real estate net, depreciable real estate reserves, loss on early extinguishment of debt, and gain on sale of marketable securities	$ 52,769	$ 113,823
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	17,166	(6,440)
Purchase price and other fair value adjustments	(2,041)	49,293
Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate	(1,049)	23,521
Net income	$ 52,769	$ 113,823

Uncategorized Items - slg-20190

Label	Element	Value
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 570,524,000