Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Operating Activities
Net income		$ 62,734	$ 224,941
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		331,117	737,195
Equity in net income from unconsolidated joint ventures		(14,104)	(11,969)
Distributions of cumulative earnings from unconsolidated joint ventures		19,609	19,311
Equity in net gain on sale of interest in unconsolidated joint venture interest/real estate		(16,166)	(43,588)
Depreciable real estate reserves		85,336	10,387
Loss (gain) on sale of real estate, net		3,256	(210,750)
(Gain) loss on sale of investments in marketable securities		(3,262)	83
Deferred rents receivable		(33,523)	40,056
Other non-cash adjustments	[1]	18,423	(155,558)
Changes in operating assets and liabilities:
Restricted cash—operations		6,520	(12,855)
Tenant and other receivables		(2,318)	2,714
Related party receivables		(8,238)	(4,167)
Deferred lease costs		(31,479)	(47,036)
Other assets		(58,068)	(30,899)
Accounts payable, accrued expenses, other liabilities and security deposits		1,423	(28,089)
Deferred revenue and land leases payable		55,361	19,016
Net cash provided by operating activities		416,621	508,792
Investing Activities
Acquisitions of real estate property		(25,114)	(38,005)
Additions to land, buildings and improvements		(251,158)	(269,182)
Escrowed cash—capital improvements/acquisition deposits/deferred purchase price		17,431	85,983
Investments in unconsolidated joint ventures		(112,697)	(69,422)
Distributions in excess of cumulative earnings from unconsolidated joint ventures		279,478	171,472
Net proceeds from disposition of real estate/joint venture interest		116,983	2,419,841
Proceeds from sale or redemption of marketable securities		55,129	6,868
Purchases of marketable securities		0	(23,062)
Other investments		46,955	8,232
Origination of debt and preferred equity investments		(935,724)	(554,803)
Repayments or redemption of debt and preferred equity investments		707,676	667,251
Net cash (used in) provided by investing activities		(101,041)	2,405,173
Financing Activities
Proceeds from mortgages and other loans payable		779,650	256,207
Repayments of mortgages and other loans payable		(706,056)	(1,786,034)
Proceeds from revolving credit facility and senior unsecured notes		1,447,800	1,260,300
Repayments of revolving credit facility and senior unsecured notes		(1,270,804)	(2,269,604)
Proceeds from stock options exercised and DRIP issuance		12,475	12,404
Repurchase of common stock		(349,991)	0
Redemption of preferred stock		(125)	(2,999)
Distributions to noncontrolling interests in other partnerships		(45,089)	(11,023)
Contributions from noncontrolling interests in other partnerships		33,202	2,019
Distributions to noncontrolling interests in the Operating Partnership		(10,639)	(9,245)
Dividends / Distributions paid on common and preferred stock / units		(251,701)	(234,801)
Other obligations related to loan participations		16,737	59,150
Deferred loan costs and capitalized lease obligation		(8,993)	(39,842)
Net cash used in financing activities		(353,534)	(2,763,468)
Net (decrease) increase in cash and cash equivalents		(37,954)	150,497
Cash and cash equivalents at beginning of year		279,443	255,399
Cash and cash equivalents at end of period		241,489	405,896
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership		23,273	51,647
Redemption of units in the Operating Partnership for stock		15,352	12,746
Derivative instruments at fair value		7,362	0
Exchange of debt investment for equity in joint venture		0	68,581
Issuance of preferred units relating to a real estate acquisition		0	22,793
Tenant improvements and capital expenditures payable		8,926	4,281
Fair value adjustment to noncontrolling interest in Operating Partnership		2,669	4,959
Deconsolidation of subsidiaries		328,643	1,173,570
Transfer of assets related to assets held for sale		273,455	2,048,376
Transfer of liabilities related to assets held for sale		1,290	1,677,528
Deferred leasing payable		810	1,208
Transfer of assets related to assets held for sale		11,158	22,179
Issuance of SLG's common stock to consolidated joint venture		0
SL Green Operating Partnership
Operating Activities
Net income		62,734	224,941
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		331,117	737,195
Equity in net income from unconsolidated joint ventures		(14,104)	(11,969)
Distributions of cumulative earnings from unconsolidated joint ventures		19,609	19,311
Equity in net gain on sale of interest in unconsolidated joint venture interest/real estate		(16,166)	(43,588)
Depreciable real estate reserves		85,336	10,387
Loss (gain) on sale of real estate, net		3,256	(210,750)
(Gain) loss on sale of investments in marketable securities		(3,262)	83
Deferred rents receivable		(33,523)	40,056
Other non-cash adjustments	[1]	18,423	(155,558)
Changes in operating assets and liabilities:
Restricted cash—operations		6,520	(12,855)
Tenant and other receivables		(2,318)	2,714
Related party receivables		(8,238)	(4,167)
Deferred lease costs		(31,479)	(47,036)
Other assets		(58,068)	(30,899)
Accounts payable, accrued expenses, other liabilities and security deposits		1,423	(28,089)
Deferred revenue and land leases payable		55,361	19,016
Net cash provided by operating activities		416,621	508,792
Investing Activities
Acquisitions of real estate property		(25,114)	(38,005)
Additions to land, buildings and improvements		(251,158)	(269,182)
Escrowed cash—capital improvements/acquisition deposits/deferred purchase price		17,431	85,983
Investments in unconsolidated joint ventures		(112,697)	(69,422)
Distributions in excess of cumulative earnings from unconsolidated joint ventures		279,478	171,472
Net proceeds from disposition of real estate/joint venture interest		116,983	2,419,841
Proceeds from sale or redemption of marketable securities		55,129	6,868
Purchases of marketable securities		0	(23,062)
Other investments		46,955	8,232
Origination of debt and preferred equity investments		(935,724)	(554,803)
Repayments or redemption of debt and preferred equity investments		707,676	667,251
Net cash (used in) provided by investing activities		(101,041)	2,405,173
Financing Activities
Proceeds from mortgages and other loans payable		779,650	256,207
Repayments of mortgages and other loans payable		(706,056)	(1,786,034)
Proceeds from revolving credit facility and senior unsecured notes		1,447,800	1,260,300
Repayments of revolving credit facility and senior unsecured notes		(1,270,804)	(2,269,604)
Proceeds from stock options exercised and DRIP issuance		12,475	12,404
Repurchase of common stock		(349,991)	0
Redemption of preferred stock		(125)	(2,999)
Distributions to noncontrolling interests in other partnerships		(45,089)	(11,023)
Contributions from noncontrolling interests in other partnerships		33,202	2,019
Dividends / Distributions paid on common and preferred stock / units		(262,340)	(244,046)
Other obligations related to loan participations		16,737	59,150
Deferred loan costs and capitalized lease obligation		(8,993)	(39,842)
Net cash used in financing activities		(353,534)	(2,763,468)
Net (decrease) increase in cash and cash equivalents		(37,954)	150,497
Cash and cash equivalents at beginning of year		279,443	255,399
Cash and cash equivalents at end of period		241,489	405,896
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of units in the Operating Partnership		23,273	51,647
Redemption of units in the Operating Partnership for stock		15,352	12,746
Derivative instruments at fair value		7,362	0
Exchange of debt investment for equity in joint venture		0	68,581
Issuance of preferred units relating to a real estate acquisition		0	22,793
Tenant improvements and capital expenditures payable		8,926	4,281
Fair value adjustment to noncontrolling interest in Operating Partnership		2,669	4,959
Deconsolidation of subsidiaries		328,643	1,173,570
Transfer of assets related to assets held for sale		273,455	2,048,376
Transfer of liabilities related to assets held for sale		1,290	1,677,528
Deferred leasing payable		810	1,208
Transfer of assets related to assets held for sale		$ 11,158	$ 22,179

[1] Included in Other non-cash adjustments is $172.4 million for the nine months ended September 30, 2016 for the amortization of the below-market lease at 388-390 Greenwich Street as a result of the tenant exercising their option to purchase the property and entering into an agreement to accelerate the sale.