Consolidated Statements of Capital - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest		$ (29,817)		$ (29,817)
DRSPP proceeds	$ 97	140	$ 439	339
Reallocation of noncontrolling interest in the Operating Partnership	3,126	28,624	(8,072)	23,539
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	7,957	8,616	22,961	22,147
Repurchases of common units				(151,197)
Contribution to consolidated joint venture interests	3,266	817	11,714	52,164
Cash distributions to noncontrolling interests	$ (851)	$ (148)	$ (1,614)	$ (3,168)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)	3	3	15	6
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)	8	11	3	215
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings				$ 3
Repurchases of common units (in units)				(1,971)
Repurchases of common units				$ (20)
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest		(75)		(75)
Contribution to consolidated joint venture interests	3,266	817	$ 11,714	52,164
Cash distributions to noncontrolling interests	(851)	(148)	(1,614)	(3,168)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning balance	4,159,833	4,748,764	4,646,922	4,778,253	$ 4,778,253
Net income (loss)	(22,023)	10,122	(417,138)	(15,266)
Acquisition of subsidiary interest from noncontrolling interest		(29,817)		(29,817)
Other comprehensive income	11,847	48,979	20,012	104,332
Preferred distributions	(3,738)	(3,738)	(11,213)	(11,213)
DRSPP proceeds	97	140	439	339
Reallocation of noncontrolling interest in the Operating Partnership	3,126	28,624	(8,072)	23,539
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	7,957	8,616	22,961	22,147
Repurchases of common units				(151,197)
Contribution to consolidated joint venture interests	3,266	817	11,714	52,164
Cash distributions to noncontrolling interests	(851)	(148)	(1,614)	(3,168)
Issuance of special distribution paid primarily in units				160,620
Cash distributions declared	(52,271)	(60,138)	(156,768)	(178,512)
Ending balance	4,107,243	4,752,221	4,107,243	4,752,221	4,646,922
SL Green Operating Partnership | Series I Preferred Units | Series I Preferred Stock
Increase (Decrease) in Partner's Capital
Beginning balance	221,932	221,932	221,932	221,932	221,932
Ending balance	221,932	221,932	221,932	221,932	221,932
SL Green Operating Partnership | Common Stock | Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning balance	$ 3,813,223	$ 4,453,271	$ 4,313,497	$ 4,589,702	$ 4,589,702
Beginning balance (units)	64,387	64,302	64,380	64,105	64,105
Net income (loss)	$ (20,229)	$ 11,115	$ (412,679)	$ (17,535)
Acquisition of subsidiary interest from noncontrolling interest		(29,742)		(29,742)
Preferred distributions	$ (3,738)	$ (3,738)	$ (11,213)	$ (11,213)
DRSPP proceeds (in shares)	3	3	15	6
DRSPP proceeds	$ 97	$ 140	$ 439	$ 339
Reallocation of noncontrolling interest in the Operating Partnership	$ 3,126	$ 28,624	$ (8,072)	$ 23,539
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)	8	11	3	215
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	$ 7,957	$ 8,616	$ 22,961	$ 22,147
Repurchases of common units (in units)				(1,971)
Repurchases of common units				$ (151,197)
Issuance of special distribution paid primarily in units (in shares)				1,961
Issuance of special distribution paid primarily in units				$ 160,620
Cash distributions declared	(52,271)	(60,138)	(156,768)	(178,512)
Ending balance	$ 3,748,165	$ 4,408,148	$ 3,748,165	$ 4,408,148	$ 4,313,497
Ending balance (units)	64,398	64,316	64,398	64,316	64,380
SL Green Operating Partnership | Accumulated Other Comprehensive Loss
Increase (Decrease) in Partner's Capital
Beginning balance	$ 57,769	$ 8,595	$ 49,604	$ (46,758)	$ (46,758)
Other comprehensive income	11,847	48,979	20,012	104,332
Ending balance	69,616	57,574	69,616	57,574	49,604
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning balance	66,909	64,966	61,889	13,377	13,377
Net income (loss)	(1,794)	(993)	(4,459)	2,269
Acquisition of subsidiary interest from noncontrolling interest		(75)		(75)
Contribution to consolidated joint venture interests	3,266	817	11,714	52,164
Cash distributions to noncontrolling interests	(851)	(148)	(1,614)	(3,168)
Ending balance	$ 67,530	$ 64,567	$ 67,530	$ 64,567	$ 61,889