Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Basic Earnings:
(Loss) income attributable to SL Green common stockholders	$ (43,876)	$ 105,332	$ (36,125)	$ 97,868
Less: distributed earnings allocated to participating securities	(497)	(362)	(995)	(725)
Less: undistributed earnings allocated to participating securities	0	(261)	0	0
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(44,373)	104,709	(37,120)	97,143
Effect of Dilutive Securities:
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	(1,103)	362	(806)	725
Add back: undistributed earnings allocated to participating securities	0	261	0	0
Add back: effect of dilutive securities (redemption of units to common shares)	(2,813)	6,282	(2,321)	5,806
Diluted Earnings:
Net (loss) income attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (48,289)	$ 111,614	$ (40,247)	$ 103,674
Basic Shares:
Weighted average common shares outstanding (shares)	63,798,000	66,931,000	63,987,000	66,948,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	4,102,000	4,093,000	4,112,000	4,121,000
Stock-based compensation plans (shares)	1,120,000	648,000	1,139,000	616,000
Contingently issuable shares (in shares)	0	0	184,000	153,000
Diluted weighted average common stock outstanding (shares)	69,020,000	71,672,000	69,422,000	71,838,000
Common stock shares excluded from the diluted shares outstanding (shares)	528,607	964,338	482,130	1,033,173