Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Basic (Loss) Earnings:
(Loss) income attributable to SL Green common stockholders	$ (111,860)	$ 7,060	$ (579,509)
Less: distributed earnings allocated to participating securities	(1,902)	(1,835)	(2,655)
Less: undistributed earnings allocated to participating securities	0	(64)	0
Net (loss) income attributable to SL Green common stockholders (numerator for basic earnings per share)	(113,762)	5,161	(582,164)
Effect of Dilutive Securities:
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0	0
Add back: undistributed earnings allocated to participating securities	0	0	0
Add back: effect of dilutive securities (redemption of units to common shares)	0	0	(37,465)
Net (loss) income attributable to SL Green common stockholders, diluted	$ (113,762)	$ 5,161	$ (619,629)
Basic Shares:
Weighted average common stock outstanding (in shares)	70,443,000	65,062,000	63,809,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (in shares)	0	0	4,163,000
Stock-based compensation plans (in shares)	0	626,000	0
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