Partners' Capital of the Operating Partnership - Additional Information (Details)		12 Months Ended
		Dec. 31, 2021 shares	Dec. 31, 2020 unit shares	Dec. 31, 2019 shares	Dec. 31, 2018 shares
Common Stock
Stockholders' Equity
Units, outstanding (in units)	[1]	64,105,000	66,474,000	74,672,000	78,897,000
SL Green Operating Partnership
Stockholders' Equity
Number of units of operating partnership owned by the noncontrolling interest unit holders (units)		3,781,565	3,938,823
SL Green Operating Partnership | Series I Preferred Units
Stockholders' Equity
Units, outstanding (in units)		9,200,000
Common units redemption, period of restriction		1 year
Conversion of stock, shares issued (in shares)		1
SL Green Operating Partnership | Common Stock
Stockholders' Equity
Units, outstanding (in units)		64,105,276

[1] On January 18, 2022, we completed a reverse stock split whereby every 1.03060 SL Green common share was combined into 1 SL Green common share. We have retroactively adjusted the outstanding share counts, share activity, cash distributions declared, and earnings per share, as if the reverse split occurred on December 31, 2018.