Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Basic Loss:
Less: distributed earnings allocated to participating securities	$ (326)	$ (362)
Net loss attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(84,717)	(21,437)
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0
Loss attributable to SL Green common stockholders (numerator for diluted earnings per share)	(84,717)	(21,437)
SL Green Operating Partnership
Basic Loss:
Net loss attributable to SLGOP common unitholders	(91,069)	(22,540)
Less: distributed earnings allocated to participating securities	(861)	(1,243)
Less: undistributed earnings allocated to participating securities	0	0
Net loss attributable to SLGOP common unitholders (numerator for basic earnings per unit)	(91,930)	(23,783)
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	0	0
Add back: undistributed earnings allocated to participating securities	0	0
Loss attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ (91,930)	$ (23,783)
Denominator
Basic weighted average common units outstanding (in shares)	75,667	74,527
Stock-based compensation plans (in shares)	0	0
Contingently issuable units (in shares)	0	0
Diluted weighted average common units outstanding (in shares)	75,667	74,527