Consolidated Statements of Capital - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest			$ (5,674)
DRSPP proceeds	$ 43	$ 158	120	$ 342
Reallocation of noncontrolling interest in the Operating Partnership	364	(1,051)	(42,477)	(11,198)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	5,578	7,445	10,179	15,004
Contributions to consolidated joint venture interests			1,823
Consolidation of joint venture interest	1,823	(112)	6,678	8,448
Cash distributions to noncontrolling interests	(1,524)	(627)	(2,807)	(763)
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable		23,582	(748)	25,919
Net income (loss) attributable to SL Green	$ 1,577	$ (356,457)	$ 18,456	$ (392,450)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)		7	2	12
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)	8	7	86	(5)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings
Common Stock | Partners' Interest
Increase (Decrease) in Partner's Capital
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable	153
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	1,823	(112)	6,678	$ 8,448
Cash distributions to noncontrolling interests	(1,524)	(627)	(2,807)	(763)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning balance	3,803,648	4,529,174	3,855,925	4,646,922	$ 4,646,922
Net income (loss)	(447)	(381,079)	16,039	(421,034)
Acquisition of subsidiary interest from noncontrolling interest			(5,674)
Other comprehensive income (loss)	220	38,341	22,894	8,165
Perpetual preferred unit dividends	(3,737)	(3,737)	(7,475)	(7,475)
DRSPP proceeds	43	158	120	342
Reallocation of noncontrolling interest in the Operating Partnership	364	(1,051)	(42,477)	(11,198)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	5,578	7,445	10,179	15,004
Contributions to consolidated joint venture interests			1,823
Consolidation of joint venture interest	1,823	(112)	6,678	8,448
Cash distributions to noncontrolling interests	(1,524)	(627)	(2,807)	(763)
Cash distributions declared	(48,360)	(52,261)	(96,716)	(104,497)
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable	153	23,582	(748)	25,919
Net income (loss) attributable to SL Green		(380,039)	19,204	(418,369)
Ending balance	3,757,761	4,159,833	3,757,761	4,159,833	3,855,925
SL Green Operating Partnership | Preferred stock | 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
Increase (Decrease) in Partner's Capital
Net income (loss)	1,424
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable	153	23,582	(748)
SL Green Operating Partnership | Common Stock | Partners' Interest
Increase (Decrease) in Partner's Capital
Beginning balance	$ 3,473,528	$ 4,219,126	$ 3,546,906	$ 4,313,497	$ 4,313,497
Beginning balance (units)	64,806	64,373	64,726	64,380	64,380
Net income (loss)		$ (380,039)	$ 19,204	$ (418,369)
Perpetual preferred unit dividends	$ (3,737)	$ (3,737)	$ (7,475)	$ (7,475)
DRSPP proceeds (in shares)		7	2	12
DRSPP proceeds	43	$ 158	$ 120	$ 342
Reallocation of noncontrolling interest in the Operating Partnership	$ 364	$ (1,051)	$ (42,477)	$ (11,198)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)	8	7	86	(5)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	$ 5,578	$ 7,445	$ 10,179	$ 15,004
Cash distributions declared	(48,360)	(52,261)	(96,716)	(104,497)
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable				25,919
Net income (loss) attributable to SL Green	1,424
Ending balance	$ 3,428,993	$ 3,813,223	$ 3,428,993	$ 3,813,223	$ 3,546,906
Ending balance (units)	64,814	64,387	64,814	64,387	64,726
SL Green Operating Partnership | Accumulated Other Comprehensive Loss
Increase (Decrease) in Partner's Capital
Beginning balance	$ 40,151	$ 19,428	$ 17,477	$ 49,604	$ 49,604
Other comprehensive income (loss)	220	38,341	22,894	8,165
Ending balance	40,371	57,769	40,371	57,769	17,477
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning balance	68,037	68,688	69,610	61,889	61,889
Net income (loss)	(1,871)	(1,040)	(3,165)	(2,665)
Acquisition of subsidiary interest from noncontrolling interest			(5,674)
Contributions to consolidated joint venture interests			1,823
Consolidation of joint venture interest	1,823	(112)	6,678	8,448
Cash distributions to noncontrolling interests	(1,524)	(627)	(2,807)	(763)
Ending balance	$ 66,465	$ 66,909	$ 66,465	$ 66,909	$ 69,610