Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Numerator
Less: distributed earnings allocated to participating securities	$ (521)	$ (436)	$ (1,042)	$ (872)
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(11,613)	(2,596)	(33,209)	10,109
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0	0	(436)
Net Income (Loss) Available to Common Stockholders, Diluted	(11,613)	(2,695)	(33,209)	11,293
SL Green Operating Partnership
Numerator
Net (loss) income attributable to SLGOP common unitholders	(11,867)	(2,313)	(34,407)	11,729
Less: distributed earnings allocated to participating securities	(1,243)	(436)	(2,486)	(872)
Net (loss) income attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(13,110)	(2,749)	(36,893)	10,857
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0	0	436
Net Income (Loss) Available to Common Stockholders, Diluted	$ (13,110)	$ (2,749)	$ (36,893)	$ 11,293
Denominator
Basic weighted average common units outstanding (in shares)	74,455	68,740	74,491	68,753
Stock-based compensation plans (shares)	0	0	0	1,384
Diluted weighted average common units outstanding (shares)	74,455	68,740	74,491	70,137