Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Basic Loss:
Loss attributable to SL Green common stockholders	$ (84,391)	$ (21,075)
Less: distributed earnings allocated to participating securities	(326)	(362)
Net loss attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(84,717)	(21,437)
Effect of Dilutive Securities:
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0
Add back: effect of dilutive securities (redemption of units to common shares)	0	0
Loss attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (84,717)	$ (21,437)
Basic Shares:
Weighted average common shares outstanding (shares)	70,687,000	70,424,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	0	0
Stock-based compensation plans (shares)	0	0
Diluted weighted average common stock outstanding (shares)	70,687,000	70,424,000
Common stock shares excluded from the diluted shares outstanding (shares)	7,375,635	6,262,427