Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Basic (Loss) Earnings:
(Loss) income attributable to SL Green common stockholders	$ (11,092)	$ (2,160)	$ (32,167)	$ 10,981
Less: distributed earnings allocated to participating securities	(521)	(436)	(1,042)	(872)
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(11,613)	(2,596)	(33,209)	10,109
Effect of Dilutive Securities:
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0	0	436
Add back: effect of dilutive securities (redemption of units to common shares)	0	(99)	0	748
Diluted Earnings:
(Loss) income attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (11,613)	$ (2,695)	$ (33,209)	$ 11,293
Basic Shares:
Weighted average common shares outstanding (shares)	70,436,000	64,353,000	70,430,000	64,340,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	0	4,387,000	0	4,413,000
Stock-based compensation plans (shares)	0	0	0	1,384,000
Diluted weighted average common stock outstanding (shares)	70,436,000	68,740,000	70,430,000	70,137,000
Common stock shares excluded from the diluted shares outstanding (shares)	352,917	1,574,571	352,917	135,000