Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator
Less: distributed earnings allocated to participating securities	$ (505)	$ (357)	$ (1,516)	$ (1,071)
Less: undistributed earnings allocated to participating securities	0	(1,977)	0	(1,790)
Net income (loss) attributable to SLGOP common unitholders (numerator for basic earnings per unit)	6,872	385,871	(30,264)	483,212
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	(505)	(357)	484	(1,071)
Add back: undistributed earnings allocated to participating securities	0	(1,977)	0	(1,790)
Net income (loss) attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ 7,868	$ 410,888	$ (32,579)	$ 514,562
Denominator
Common stock shares excluded from the diluted shares outstanding (shares)	621,134	969,631	517,574	1,032,243
SL Green Operating Partnership
Numerator
Net income (loss) attributable to SLGOP common unitholders (numerator for diluted earnings per unit)	$ 7,868	$ 410,888	$ (30,579)	$ 514,562
Less: distributed earnings allocated to participating securities	(505)	(357)	(1,516)	(1,071)
Less: undistributed earnings allocated to participating securities	0	(1,977)	0	(1,790)
Net income (loss) attributable to SLGOP common unitholders (numerator for basic earnings per unit)	7,363	408,554	(32,095)	511,701
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	505	357	(484)	1,071
Add back: undistributed earnings allocated to participating securities	0	1,977	0	1,790
Net income (loss) attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ 7,868	$ 410,888	$ (32,579)	$ 514,562
Denominator
Basic weighted average common units outstanding (in shares)	68,037,000	68,690,000	68,075,000	70,272,000
Stock-based compensation plans (shares)	860,000	806,000	1,052,000	676,000
Contingently issuable units (in shares)	0	0	122,000	101,000
Diluted weighted average common units outstanding (shares)	68,897,000	69,496,000	69,249,000	71,049,000
Common stock shares excluded from the diluted shares outstanding (shares)	621,134	969,631	517,574	1,032,243