Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator
Less: distributed earnings allocated to participating securities	$ (406)	$ (335)
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(40,137)	7,416
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	96
Net (loss) income attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (42,974)	$ 7,812
Denominator
Common stock shares excluded from the diluted shares outstanding (shares)	1,275,225	351,927
SL Green Operating Partnership
Numerator
Net (loss) income attributable to SLGOP common unitholders (numerator for diluted earnings per unit)	$ (42,068)	$ 8,243
Less: distributed earnings allocated to participating securities	(906)	(335)
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(42,974)	7,908
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	(96)
Net (loss) income attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (42,974)	$ 7,812
Denominator
Basic weighted average common units outstanding (in shares)	68,182,000	68,470,000
Stock-based compensation plans (shares)	0	984,000
Contingently issuable units (in shares)	0	774,000
Diluted weighted average common units outstanding (shares)	68,182,000	70,228,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,275,225	351,927