Consolidated Statements of Capital - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest	$ (15,631)		$ (15,631)	$ (5,674)
DRSPP proceeds	56	$ 43	131	120
Conversion of common units	0	0	0
Measurement adjustment for redeemable noncontrolling interest	(9,955)		(22,895)	0
Reallocation of noncontrolling interest in the Operating Partnership	0	364	0	(42,477)
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	5,982	5,578	3,457	10,179
Proceeds from issuance of common stock			(871)
Repurchases of common units			0	0
Proceeds from stock options exercised			0	0
Contributions to consolidated joint venture interests	1,310	1,823	4,747	1,823
Contributions to debt fund investments	24,193		24,193
Consolidation of joint venture interest	0		0	6,678
Cash distributions to noncontrolling interests	$ (1,380)	$ (1,524)	$ (1,601)	$ (2,807)
Common Stock
Increase (Decrease) in Partner's Capital
DRSPP proceeds (in shares)	1		2	2
DRSPP proceeds
Conversion of common units (shares)	1		5
Conversion of common units
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in units)	7	8	(79)	86
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings			$ (1)
Repurchases of common units
Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Acquisition of subsidiary interest from noncontrolling interest	(51,654)		(51,654)	(5,674)
Contributions to consolidated joint venture interests	1,310	1,823	4,747	1,823
Contributions to debt fund investments	24,193		(24,193)
Consolidation of joint venture interest				6,678
Cash distributions to noncontrolling interests	(1,380)	(1,524)	(1,601)	(2,807)
SL Green Operating Partnership
Increase (Decrease) in Partner's Capital
Beginning balance	3,953,427	3,803,648	4,069,951	3,855,925	$ 3,855,925
Net income	(8,970)	(447)	(32,669)	16,039
Net income (loss) attributable to partnership units	775	153	2,240	(748)
Acquisition of subsidiary interest from noncontrolling interest	(15,631)		(15,631)
Acquisition of subsidiary interest from noncontrolling interest				(5,674)
Other comprehensive income (loss)	(11,482)	220	(34,520)	22,894
Perpetual preferred unit dividends	(3,737)	(3,737)	(7,475)	(7,475)
DRSPP proceeds	56	43	131	120
Conversion of common units	0		0
Measurement adjustment for redeemable noncontrolling interest			(22,895)
Reallocation of noncontrolling interest in the Operating Partnership	0	364		(42,477)
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	5,982	5,578	3,457	10,179
Proceeds from issuance of common stock			(871)
Repurchases of common units			0
Proceeds from stock options exercised			0
Contributions to consolidated joint venture interests	1,310	1,823	4,747	1,823
Consolidation of joint venture interest	0			6,678
Cash distributions to noncontrolling interests	(1,380)	(1,524)	(1,601)	(2,807)
Issuance of special distribution paid in units	0		0
Cash distributions declared	(54,485)	(48,360)	(108,954)	(96,716)
Ending balance	3,880,103	3,757,761	3,880,103	3,757,761	4,069,951
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
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	$ 3,619,367	$ 3,473,528	$ 3,711,172	$ 3,546,906	$ 3,546,906
Beginning balance (units)	71,016	64,806	71,097	64,726	64,726
Net income	$ (8,130)	$ 1,424	$ (26,932)	$ 19,204
Net income (loss) attributable to partnership units	775	153	2,240	(748)
Acquisition of subsidiary interest from noncontrolling interest	36,023		36,023
Perpetual preferred unit dividends	$ (3,737)	(3,737)	$ (7,475)	$ (7,475)
DRSPP proceeds (in shares)	1		2	2
DRSPP proceeds	$ 56	43	$ 131	$ 120
Conversion of common units (shares)	1		5
Measurement adjustment for redeemable noncontrolling interest	$ (9,955)		$ (22,895)
Reallocation of noncontrolling interest in the Operating Partnership		$ 364		$ (42,477)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in units)	7	8	(79)	86
Deferred compensation plan and unit awards, net of forfeitures and tax withholdings	$ 5,982	$ 5,578	$ 3,457	$ 10,179
Proceeds from issuance of common stock			(871)
Issuance of special distribution paid in units (in shares)	0
Issuance of special distribution paid in units	$ 0
Cash distributions declared	(54,485)	(48,360)	(108,954)	(96,716)
Ending balance	$ 3,585,896	$ 3,428,993	$ 3,585,896	$ 3,428,993	$ 3,711,172
Ending balance (units)	71,025	64,814	71,025	64,814	71,097
SL Green Operating Partnership | Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Partner's Capital
Beginning balance	$ (4,842)	$ 40,151	$ 18,196	$ 17,477	$ 17,477
Other comprehensive income (loss)	(11,482)	220	(34,520)	22,894
Ending balance	(16,324)	40,371	(16,324)	40,371	18,196
SL Green Operating Partnership | Noncontrolling Interests
Increase (Decrease) in Partner's Capital
Beginning balance	116,970	68,037	118,651	69,610	69,610
Net income	(840)	(1,871)	(5,737)	(3,165)
Acquisition of subsidiary interest from noncontrolling interest	(51,654)		(51,654)
Acquisition of subsidiary interest from noncontrolling interest				(5,674)
Contributions to consolidated joint venture interests	1,310	1,823	4,747	1,823
Contributions to debt fund investments	24,193		24,193
Consolidation of joint venture interest				6,678
Cash distributions to noncontrolling interests	(1,380)	(1,524)	(1,601)	(2,807)
Ending balance	$ 88,599	$ 66,465	$ 88,599	$ 66,465	$ 118,651