Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator
Less: distributed earnings allocated to participating securities	$ (2,655)	$ (2,219)	$ (2,398)
Less: undistributed earnings allocated to participating securities	0	0	(192)
Net (loss) income attributable to SL Green common stockholders (numerator for basic earnings per share)	(582,164)	(95,243)	432,214
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	$ 0	$ 0	$ 2,039
Denominator
Diluted weighted average common stock outstanding (in shares)	67,972,000	67,929,000	70,769,000
Common stock shares excluded from the diluted shares outstanding (in shares)	1,273,417	1,682,236	948,017
SL Green Operating Partnership
Numerator
Net (loss) income attributable to SLGOP common unitholders	$ (616,974)	$ (98,818)	$ 460,261
Less: distributed earnings allocated to participating securities	(2,655)	(2,219)	(2,398)
Less: undistributed earnings allocated to participating securities	0	0	(192)
Net (loss) income attributable to SL Green common stockholders (numerator for basic earnings per share)	(619,629)	(101,037)	457,671
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0	2,590
(Loss) income attributable to SLGOP common unitholders	$ (619,629)	$ (101,037)	$ 460,261
Denominator
Basic weighted average common units outstanding (in shares)	67,972,000	67,929,000	69,667,000
Stock-based compensation plans (in shares)	0	0	765,000
Contingently issuable units (in shares)	0	0	337,000
Diluted weighted average common stock outstanding (in shares)	67,972,000	67,929,000	70,769,000