Noncontrolling Interests on the Company's Consolidated Financial Statements - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Issuance of common and preferred units			$ 4,686	$ 1,823
Redemption and conversion of common units			(15,631)	(5,674)
Net (loss) income	$ 1,737	$ (914)	(503)	(166)
Accumulated other comprehensive (loss) income allocation	$ (229)	(4,717)	$ (2,646)	(3,097)
SL Green Operating Partnership
Organization
Number of units of operating partnership owned by the noncontrolling interest unit holders (shares)	4,849,771		4,849,771		4,509,953
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Issuance of common and preferred units	$ (61)		$ 4,686	1,823
Redemption and conversion of common units				(5,674)
Accumulated other comprehensive (loss) income allocation	$ (229)	$ (4,717)	$ (2,646)	(3,097)
SL Green Operating Partnership | Series A
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			6.00%
Number of units authorized (in shares)	109,161		109,161
Number of units issued (in shares)	109,161		109,161
Number of units outstanding (in shares)	109,161		109,161
Annual dividend per unit (in dollars per share)			$ 60.0000
Liquidation preference per unit (in dollars per share)	$ 1,000		1,000
Conversion price per unit (in dollars per share)	$ 0		$ 0
SL Green Operating Partnership | Series F
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			7.00%
Number of units authorized (in shares)	60		60
Number of units issued (in shares)	60		60
Number of units outstanding (in shares)	60		60
Annual dividend per unit (in dollars per share)			$ 70.0000
Liquidation preference per unit (in dollars per share)	$ 1,000		1,000
Conversion price per unit (in dollars per share)	$ 29.12		$ 29.12
SL Green Operating Partnership | Series K
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			3.50%
Number of units authorized (in shares)	700,000		700,000
Number of units issued (in shares)	563,954		563,954
Number of units outstanding (in shares)	341,677		341,677
Annual dividend per unit (in dollars per share)			$ 0.8750
Liquidation preference per unit (in dollars per share)	$ 25.00		25.00
Conversion price per unit (in dollars per share)	$ 134.67		$ 134.67
SL Green Operating Partnership | Series L
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			4.00%
Number of units authorized (in shares)	500,000		500,000
Number of units issued (in shares)	378,634		378,634
Number of units outstanding (in shares)	272,783		272,783
Annual dividend per unit (in dollars per share)			$ 1.0000
Liquidation preference per unit (in dollars per share)	$ 25.00		25.00
Conversion price per unit (in dollars per share)	$ 0		$ 0
SL Green Operating Partnership | Series R
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			3.50%
Number of units authorized (in shares)	400,000		400,000
Number of units issued (in shares)	400,000		400,000
Number of units outstanding (in shares)	400,000		400,000
Annual dividend per unit (in dollars per share)			$ 0.8750
Liquidation preference per unit (in dollars per share)	$ 25.00		25.00
Conversion price per unit (in dollars per share)	$ 154.89		$ 154.89
SL Green Operating Partnership | Series S
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			4.00%
Number of units authorized (in shares)	1,077,280		1,077,280
Number of units issued (in shares)	1,077,280		1,077,280
Number of units outstanding (in shares)	1,077,280		1,077,280
Annual dividend per unit (in dollars per share)			$ 1.0000
Liquidation preference per unit (in dollars per share)	$ 25.00		25.00
Conversion price per unit (in dollars per share)	$ 0		$ 0
SL Green Operating Partnership | Series V
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Stated Distribution Rate			5.00%
Number of units authorized (in shares)	40,000		40,000
Number of units issued (in shares)	40,000		40,000
Number of units outstanding (in shares)	40,000		40,000
Annual dividend per unit (in dollars per share)			$ 1.2500
Liquidation preference per unit (in dollars per share)	$ 25.00		25.00
Conversion price per unit (in dollars per share)	$ 0		$ 0
SL Green Operating Partnership | Series W
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Number of units authorized (in shares)	1		1
Number of units issued (in shares)	1		1
Number of units outstanding (in shares)	1		1
Preferred stock, dividend, multiplier per common unit distribution			1,350
Partnership Interest
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period			$ 288,941	$ 238,051	$ 238,051
Distributions			(11,687)		(13,915)
Issuance of common and preferred units			14,083		20,790
Redemption and conversion of common units			(21,558)		(28,663)
Net (loss) income			(503)		497
Accumulated other comprehensive (loss) income allocation			(2,646)		151
Fair value adjustment			14,243		72,030
Balance at end of period	$ 280,873		$ 280,873		$ 288,941
Operating Partnership | SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	6.39%		6.39%		5.97%