Consolidated Statements of Capital - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Increase (Decrease) in Partner's Capital
Net income attributable to partnership units		$ 1,574		$ 166	$ 27,493
Acquisition of subsidiary interest from noncontrolling interest				(5,674)
DRSPP proceeds	$ 23,633	97		23,753	439
Conversion of units in the Operating Partnership for common stock	0		$ 0
Reallocation of noncontrolling interest in the Operating Partnership	(34,923)	3,126		(77,400)	(8,072)
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	5,707	7,957		15,886	22,961
Contributions to consolidated joint venture interests				1,823
Consolidation of joint venture interest		3,266		6,678	11,714
Cash distributions to noncontrolling interests	$ (1,760)	$ (851)		$ (4,567)	$ (1,614)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)	340	3		342	15
DRSPP proceeds	$ 3			$ 3
Conversion of common units (shares)	77		77
Conversion of units in the Operating Partnership for common stock
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in units)	4	8		90	3
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings
Common Stock \| Partners' Interest
Increase (Decrease) in Partner's Capital
Net income attributable to partnership units	914
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest				$ (5,674)
Contributions to consolidated joint venture interests				1,823
Consolidation of joint venture interest		3,266		6,678	$ 11,714
Cash distributions to noncontrolling interests	(1,760)	(851)		(4,567)	(1,614)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning balance	3,757,761	4,159,833	$ 4,646,922	3,855,925	4,646,922	$ 4,646,922
Net income (loss)	(11,440)	(22,023)		4,599	(417,138)
Net income attributable to partnership units	914			166
Acquisition of subsidiary interest from noncontrolling interest				(5,674)
Other comprehensive income (loss)	(67,679)	11,847		(44,785)	20,012
Perpetual preferred unit dividends	(3,738)	(3,738)		(11,213)	(11,213)
DRSPP proceeds	23,633	97		23,753	439
Conversion of units in the Operating Partnership for common stock			0	0
Reallocation of noncontrolling interest in the Operating Partnership	(34,923)	3,126		(77,400)	(8,072)
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	5,707	7,957		15,886	22,961
Contributions to consolidated joint venture interests				1,823
Consolidation of joint venture interest		3,266		6,678	11,714
Cash distributions to noncontrolling interests	(1,760)	(851)		(4,567)	(1,614)
Cash distributions declared	(48,470)	(52,271)		(145,186)	(156,768)
Ending balance	3,620,005	4,107,243	4,159,833	3,620,005	4,107,243	3,855,925
SL Green Operating Partnership \| Series I Preferred Stock \| Series I Preferred Stock
Increase (Decrease) in Partner's Capital
Beginning balance	221,932	221,932	221,932	221,932	221,932	221,932
Ending balance	221,932	221,932	221,932	221,932	221,932	221,932
SL Green Operating Partnership \| Common Stock
Increase (Decrease) in Partner's Capital
Net income (loss)	(10,455)
Net income attributable to partnership units	914			166
SL Green Operating Partnership \| Common Stock \| Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning balance	$ 3,428,993	$ 3,813,223	$ 4,313,497	$ 3,546,906	$ 4,313,497	$ 4,313,497
Beginning balance (units)	64,814	64,387	64,380	64,726	64,380	64,380
Net income (loss)		$ (20,229)		$ 8,749	$ (412,679)
Perpetual preferred unit dividends	$ (3,738)	$ (3,738)		$ (11,213)	$ (11,213)
DRSPP proceeds (in shares)	340	3		342	15
DRSPP proceeds	$ 23,633	$ 97		$ 23,753	$ 439
Conversion of common units (shares)	77			77
Reallocation of noncontrolling interest in the Operating Partnership	$ (34,923)	$ 3,126		$ (77,400)	$ (8,072)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in units)	4	8		90	3
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	$ 5,707	$ 7,957		$ 15,886	$ 22,961
Cash distributions declared	(48,470)	(52,271)		(145,186)	(156,768)
Ending balance	$ 3,361,661	$ 3,748,165	$ 3,813,223	$ 3,361,661	$ 3,748,165	$ 3,546,906
Ending balance (units)	65,235	64,398	64,387	65,235	64,398	64,726
SL Green Operating Partnership \| Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning balance	$ 40,371	$ 57,769	$ 49,604	$ 17,477	$ 49,604	$ 49,604
Other comprehensive income (loss)	(67,679)	11,847		(44,785)	20,012
Ending balance	(27,308)	69,616	57,769	(27,308)	69,616	17,477
SL Green Operating Partnership \| Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning balance	66,465	66,909	61,889	69,610	61,889	61,889
Net income (loss)	(985)	(1,794)		(4,150)	(4,459)
Acquisition of subsidiary interest from noncontrolling interest				(5,674)
Contributions to consolidated joint venture interests				1,823
Consolidation of joint venture interest		3,266		6,678	11,714
Cash distributions to noncontrolling interests	(1,760)	(851)		(4,567)	(1,614)
Ending balance	$ 63,720	$ 67,530	$ 66,909	$ 63,720	$ 67,530	$ 69,610

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