Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Operating Activities
Net income	$ 480,632	$ 414,758	$ 291,487
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	228,293	325,462	284,011
Equity in net loss from unconsolidated joint ventures	55,402	25,195	34,518
Distributions of cumulative earnings from unconsolidated joint ventures	824	679	864
Equity in net loss (gain) on sale of interest in unconsolidated joint venture interest/real estate	32,757	(2,961)	(76,181)
Purchase price and other fair value adjustments	(210,070)	(187,522)	(69,389)
Depreciable real estate reserves and impairments	23,794	60,454	7,047
(Gain) loss on sale of real estate, net	(287,417)	(215,506)	16,749
Loan loss reserves and other investment reserves, net of recoveries	2,931	35,298	0
Loss on early extinguishment of debt	1,551	0	0
Deferred rents receivable	(6,701)	(7,582)	(13,941)
Non-cash lease expense	17,234	11,984	13,744
Other non-cash adjustments	37,164	15,178	271
Changes in operating assets and liabilities:
Tenant and other receivables	(20,561)	(17,074)	(4,968)
Related party receivables	(8,727)	1,451	7,802
Deferred lease costs	(10,117)	(20,900)	(70,938)
Other assets	20,345	(26,137)	(18,630)
Accounts payable, accrued expenses, other liabilities and security deposits	(66,387)	132,171	(25,597)
Deferred revenue	(1,727)	20,657	10,824
Change in lease liability - operating leases	(33,241)	(11,369)	(11,200)
Net cash provided by operating activities	255,979	554,236	376,473
Investing Activities
Acquisitions of real estate property	(152,791)	(86,846)	(262,591)
Additions to land, buildings and improvements	(302,486)	(458,140)	(252,986)
Acquisition deposits and deferred purchase price	0	0	(5,239)
Investments in unconsolidated joint ventures	(88,872)	(70,315)	(128,682)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	770,604	124,572	79,020
Net proceeds from disposition of real estate/joint venture interest	651,594	1,112,382	208,302
Cash assumed from consolidation of real estate investment	9,475	0	0
Proceeds from sale or redemption of marketable securities	4,528	0	0
Purchases of marketable securities	(10,000)	0	0
Other investments	40,200	32,479	(7,869)
Origination of debt and preferred equity investments	(95,695)	(360,953)	(607,844)
Repayments or redemption of debt and preferred equity investments	167,024	763,251	1,092,383
Net cash provided by investing activities	993,581	1,056,430	114,494
Financing Activities
Proceeds from mortgages and other loans payable	39,689	1,181,892	752,984
Repayments of mortgages and other loans payable	(375,044)	(1,186,828)	(230,076)
Proceeds from revolving credit facility and senior unsecured notes	1,488,000	1,495,000	1,310,000
Repayments of revolving credit facility and senior unsecured notes	(1,808,000)	(1,875,000)	(1,570,000)
Proceeds from stock options exercised and DRSPP issuance	1,556	1,006	334
Repurchase of common stock	(341,403)	(528,483)	(384,399)
Redemption of preferred stock	(6,040)	(82,750)	(18,142)
Redemption of OP units	(25,703)	(27,342)	(27,495)
Distributions to noncontrolling interests in other partnerships	(6,631)	(85,468)	(478)
Contributions from noncontrolling interests in other partnerships	336	12,477	10,239
Acquisition of subsidiary interest from noncontrolling interest	0	(1,536)	(25,845)
Dividends/Distributions paid on common and preferred stock/units	(271,075)	(293,996)	(306,386)
Other obligation related to secured borrowing	51,862	0	0
Tax withholdings related to restricted share awards	(2,990)	(4,752)	(3,495)
Deferred loan costs	(13,745)	(70,036)	(21,162)
Principal payments of on financing lease liabilities	(434)	(833)	0
Net cash used in financing activities	(1,285,371)	(1,479,301)	(528,650)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(35,811)	131,365	(37,683)
Cash, cash equivalents, and restricted cash at beginning of year	372,795	241,430	279,113
Cash, cash equivalents, and restricted cash at end of period	336,984	372,795	241,430
Supplemental Cash Flow Information [Abstract]
Interest paid	152,773	201,348	248,684
Income taxes paid	4,405	2,296	1,489
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Conversion of units in the Operating Partnership	0	8,744	471
Redemption of units in the Operating Partnership for a joint venture sale	27,586	0	0
Exchange of preferred equity investment for real estate or equity in joint venture	0	119,497	0
Exchange of debt investment for real estate or equity in joint venture	9,468	122,796	34,498
Assumption of mortgage loan	60,000	0	0
Tenant improvements and capital expenditures payable	7,580	1,665	6,056
Fair value adjustment to noncontrolling interest in the Operating Partnership	9,851	32,598	34,320
Deconsolidation of a subsidiary	66,837	854,437	395
Deconsolidation of a subsidiary mortgage	510,000	5,593	0
Mortgages assumed in connection with sale of real estate	0	250,000	0
Seller financed purchases	0	100,000	0
Debt and preferred equity investments	8,372	9,014	0
Transfer of assets related to assets held for sale	140,855	0	391,664
Reversal of assets held for sale	0	391,664	0
Transfer of liabilities related to assets held for sale	64,120	0	0
Extinguishment of debt in connection with property dispositions	53,548	0	0
Consolidation of real estate investment	119,444	0	0
Removal of fully depreciated commercial real estate properties	19,831	66,169	19,577
Sale of interest in partially owned entity	4,476	0	0
Contribution to consolidated joint venture by noncontrolling interest	0	0	48,223
Distributions to noncontrolling interests	358	6,613	0
Share repurchase payable	0	3,779	0
Recognition of sales-type leases and related lease liabilities	0	119,725	0
Recognition of right of use assets and related lease liabilities	537,344	61,990	389,120
Cash and cash equivalents	251,417	266,059	166,070
Restricted cash	85,567	106,736	75,360
Total cash, cash equivalents, and restricted cash	336,984	372,795	241,430
SL Green Operating Partnership
Operating Activities
Net income	480,632	414,758	291,487
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	228,293	325,462	284,011
Equity in net loss from unconsolidated joint ventures	55,402	25,195	34,518
Distributions of cumulative earnings from unconsolidated joint ventures	824	679	864
Equity in net loss (gain) on sale of interest in unconsolidated joint venture interest/real estate	32,757	(2,961)	(76,181)
Purchase price and other fair value adjustments	(210,070)	(187,522)	(69,389)
Depreciable real estate reserves and impairments	23,794	60,454	7,047
(Gain) loss on sale of real estate, net	(287,417)	(215,506)	16,749
Loan loss reserves and other investment reserves, net of recoveries	2,931	35,298	0
Loss on early extinguishment of debt	1,551	0	0
Deferred rents receivable	(6,701)	(7,582)	(13,941)
Non-cash lease expense	17,234	11,984	13,744
Other non-cash adjustments	37,164	15,178	271
Changes in operating assets and liabilities:
Tenant and other receivables	(20,561)	(17,074)	(4,968)
Related party receivables	(8,727)	1,451	7,802
Deferred lease costs	(10,117)	(20,900)	(70,938)
Other assets	20,345	(26,137)	(18,630)
Accounts payable, accrued expenses, other liabilities and security deposits	(66,387)	132,171	(25,597)
Deferred revenue	(1,727)	20,657	10,824
Change in lease liability - operating leases	(33,241)	(11,369)	(11,200)
Net cash provided by operating activities	255,979	554,236	376,473
Investing Activities
Acquisitions of real estate property	(152,791)	(86,846)	(262,591)
Additions to land, buildings and improvements	(302,486)	(458,140)	(252,986)
Acquisition deposits and deferred purchase price	0	0	(5,239)
Investments in unconsolidated joint ventures	(88,872)	(70,315)	(128,682)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	770,604	124,572	79,020
Net proceeds from disposition of real estate/joint venture interest	651,594	1,112,382	208,302
Cash assumed from consolidation of real estate investment	9,475	0	0
Proceeds from sale or redemption of marketable securities	4,528	0	0
Purchases of marketable securities	(10,000)	0	0
Other investments	40,200	32,479	(7,869)
Origination of debt and preferred equity investments	(95,695)	(360,953)	(607,844)
Repayments or redemption of debt and preferred equity investments	167,024	763,251	1,092,383
Net cash provided by investing activities	993,581	1,056,430	114,494
Financing Activities
Proceeds from mortgages and other loans payable	39,689	1,181,892	752,984
Repayments of mortgages and other loans payable	(375,044)	(1,186,828)	(230,076)
Proceeds from revolving credit facility and senior unsecured notes	1,488,000	1,495,000	1,310,000
Repayments of revolving credit facility and senior unsecured notes	(1,808,000)	(1,875,000)	(1,570,000)
Payment of debt extinguishment costs	0	0	0
Proceeds from stock options exercised and DRSPP issuance	1,556	1,006	334
Repurchase of common stock	(341,403)	(528,483)	(384,399)
Redemption of preferred stock	(6,040)	(82,750)	(18,142)
Redemption of OP units	(25,703)	(27,342)	(27,495)
Distributions to noncontrolling interests in other partnerships	(6,631)	(85,468)	(478)
Contributions from noncontrolling interests in other partnerships	336	12,477	10,239
Acquisition of subsidiary interest from noncontrolling interest	0	(1,536)	(25,845)
Dividends/Distributions paid on common and preferred stock/units	(286,824)	(306,648)	(321,115)
Other obligation related to secured borrowing	51,862	0	0
Tax withholdings related to restricted share awards	(2,990)	(4,752)	(3,495)
Deferred loan costs	(13,745)	(70,036)	(21,162)
Principal payments of on financing lease liabilities	(434)	(833)	0
Net cash used in financing activities	(1,285,371)	(1,479,301)	(528,650)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(35,811)	131,365	(37,683)
Cash, cash equivalents, and restricted cash at beginning of year	372,795	241,430	279,113
Cash, cash equivalents, and restricted cash at end of period	336,984	372,795	241,430
Supplemental Cash Flow Information [Abstract]
Interest paid	152,773	201,348	248,684
Income taxes paid	4,405	2,296	1,489
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Conversion of units in the Operating Partnership	0	8,744	471
Redemption of units in the Operating Partnership for a joint venture sale	27,586	0	0
Exchange of preferred equity investment for real estate or equity in joint venture	0	119,497	0
Exchange of debt investment for real estate or equity in joint venture	9,468	122,796	34,498
Assumption of mortgage loan	60,000	0	0
Issuance of common units relating to the real estate acquisition	121,418	0	0
Tenant improvements and capital expenditures payable	7,580	1,665	6,056
Fair value adjustment to noncontrolling interest in the Operating Partnership	9,851	32,598	34,320
Deconsolidation of a subsidiary	66,837	854,437	395
Deconsolidation of a subsidiary mortgage	510,000	5,593	0
Mortgages assumed in connection with sale of real estate	0	250,000	0
Seller financed purchases	0	100,000	0
Debt and preferred equity investments	8,372	9,014	0
Transfer of assets related to assets held for sale	140,855	0	391,664
Reversal of assets held for sale	0	391,664	0
Transfer of liabilities related to assets held for sale	64,120	0	0
Extinguishment of debt in connection with property dispositions	53,548	0	0
Consolidation of real estate investment	119,444	0	0
Removal of fully depreciated commercial real estate properties	19,831	66,169	19,577
Sale of interest in partially owned entity	4,476	0	0
Contribution to consolidated joint venture by noncontrolling interest	0	0	48,223
Distributions to noncontrolling interests	358	6,613	0
Share repurchase payable	0	3,779	0
Recognition of sales-type leases and related lease liabilities	0	119,725	0
Recognition of right of use assets and related lease liabilities	537,344	61,990	389,120
Cash and cash equivalents	251,417	266,059	166,070
Restricted cash	85,567	106,736	75,360
Total cash, cash equivalents, and restricted cash	336,984	372,795	241,430
Preferred Units
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of preferred units relating to a real estate acquisition	0	0	1,000
Preferred Units | SL Green Operating Partnership
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Issuance of preferred units relating to a real estate acquisition	$ 0	$ 0	$ 1,000