Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Basic Earnings:
Income (loss) attributable to SL Green common stockholders	$ 7,060	$ (579,509)	$ (93,024)
Less: distributed earnings allocated to participating securities	(1,835)	(2,655)	(2,219)
Less: undistributed earnings allocated to participating securities	(64)	0	0
Net income (loss) attributable to SL Green common stockholders (numerator for basic earnings per share)	5,161	(582,164)	(95,243)
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	(37,465)	(5,794)
Net (loss) income attributable to SL Green common stockholders, diluted	$ 5,161	$ (619,629)	$ (101,037)
Basic Shares:
Weighted average common stock outstanding (in shares)	65,062,000	63,809,000	63,917,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (in shares)	0	4,163,000	4,012,000
Stock-based compensation plans (in shares)	626,000	0	0
Diluted weighted average common stock outstanding (in shares)	65,688,000	67,972,000	67,929,000
Common stock shares excluded from the diluted shares outstanding (in shares)	4,717,759