Stockholders' Equity of the Company - Earnings per Share (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic Earnings:
Income attributable to SL Green common stockholders	$ 434,804	$ 356,105	$ 255,484
Net income attributable to SL Green common stockholders (numerator for basic earnings per share)	432,214	354,283	253,784
Effect of Dilutive Securities:
Add back: dilutive effect of earnings allocated to participating securities and contingently issuable shares	2,039	1,685	1,700
Add back: undistributed earnings allocated to participating securities	192	137	0
Add back: Effect of dilutive securities (redemption of units to common shares)	25,457	20,016	13,301
Diluted Earnings:
Income attributable to SL Green common stockholders (numerator for diluted earnings per share)	$ 459,902	$ 376,121	$ 268,785
Basic Shares:
Weighted average common stock outstanding (in shares)	65,740,000	70,397,000	77,057,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (in shares)	3,987,000	4,096,000	4,275,000
Stock-based compensation plans (in shares)	705,000	441,000	533,000
Contingently issuable shares from special dividend declared December 4, 2020 (in shares)	337,000	144,000	0
Diluted weighted average common stock outstanding (in shares)	70,769,000	75,078,000	81,865,000
Common stock shares excluded from the diluted shares outstanding (shares)	948,017	1,676,825	1,181,014