Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Basic Earnings (Loss):
Less: distributed earnings allocated to participating securities	$ (323)	$ (519)	$ (975)	$ (1,561)
Less: undistributed earnings allocated to participating securities	(531)	0	0	0
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	719	0	0	0
Income (loss) attributable to SL Green common stockholders (numerator for diluted earnings per share)	76,725	24,355	(39,677)	(8,854)
SL Green Operating Partnership
Basic Earnings (Loss):
Net income (loss) attributable to SLGOP common unitholders	77,989	26,611	(41,738)	(7,796)
Less: distributed earnings allocated to participating securities	(815)	(1,239)	(2,536)	(3,725)
Less: undistributed earnings allocated to participating securities	(531)	0	0	0
Net income (loss) attributable to SLGOP common unitholders (numerator for basic earnings per unit)	76,643	25,372	(44,274)	(11,521)
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	719	213	0	0
Income (loss) attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ 77,362	$ 25,585	$ (44,274)	$ (11,521)
Denominator
Basic weighted average common units outstanding (in shares)	75,051	74,318	75,412	74,433
Stock-based compensation plans (in shares)	312	798	0	0
Contingently issuable shares (in shares)	609	519	0	0
Diluted weighted average common units outstanding (in shares)	75,972	75,635	75,412	74,433

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