Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Basic (Loss) Earnings:
Less: distributed earnings allocated to participating securities	$ (1,902)	$ (1,835)	$ (2,655)
Net (loss) income attributable to SL Green common stockholders (numerator for basic earnings per share)	(113,762)	5,161	(582,164)
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	$ 0	$ 0	$ 0
Effect of Dilutive Securities:
Diluted weighted average common stock outstanding (in shares)	70,443,000	65,688,000	67,972,000
Common stock shares excluded from the diluted shares outstanding (in shares)	6,377,684	4,717,759	1,273,417
SL Green Operating Partnership
Basic (Loss) Earnings:
Net (Loss) income attributable to SLGOP common unitholders (numerator for diluted earnings per unit)	$ (119,533)	$ 7,557	$ (616,974)
Less: distributed earnings allocated to participating securities	(4,545)	(4,665)	(2,655)
Net (loss) income attributable to SL Green common stockholders (numerator for basic earnings per share)	(124,078)	2,892	(619,629)
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	26	0
(Loss) income attributable to SLGOP common unitholders	$ (124,078)	$ 2,918	$ (619,629)
Basic units:
Basic weighted average common units outstanding (in shares)	74,407,000	68,736,000	67,972,000
Effect of Dilutive Securities:
Stock-based compensation plans (in shares)	0	757,000	0
Contingently issuable units (in shares)	0	112,000	0
Diluted weighted average common stock outstanding (in shares)	74,407,000	69,605,000	67,972,000
Common stock shares excluded from the diluted shares outstanding (in shares)	2,413,479	800,881	1,273,417