Stockholders' Equity of the Company - Additional Information (Details)					1 Months Ended			12 Months Ended
		Jan. 18, 2022	Jan. 10, 2022	Dec. 02, 2021 $ / shares	Dec. 31, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2021 $ / shares shares	Dec. 31, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2018 shares
Class of Stock [Line Items]
Authorized capital stock (in shares) | shares					260,000,000			260,000,000
Authorized shares, par value (in dollars per share)					$ 0.01			$ 0.01
Common stock, shares authorized (in shares) | shares					160,000,000	160,000,000		160,000,000	160,000,000
Common stock, par value (in dollars per share)					$ 0.01	$ 0.01		$ 0.01	$ 0.01
Excess stock, shares authorized (shares) | shares					75,000,000			75,000,000
Excess stock, par value (in dollars per share)					$ 0.01			$ 0.01
Preferred stock, shares authorized (shares) | shares					25,000,000			25,000,000
Preferred stock, par (in dollars per share)					$ 0.01			$ 0.01
Excess shares issued (shares) | shares					0			0
Cash distribution declared, per common share (in dollars per share)					$ 0.3203	$ 0.3217	$ 0.9387	$ 6.2729	4.9374	$ 3.6434
Ordinary Dividend
Class of Stock [Line Items]
Cash distribution declared, per common share (in dollars per share)				$ 0.3108
Special Dividend
Class of Stock [Line Items]
Cash distribution declared, per common share (in dollars per share)				$ 2.4392
SL Green Operating Partnership
Class of Stock [Line Items]
Cash distribution declared, per common share (in dollars per share)								$ 6.2729	$ 4.9374	$ 3.6434
Common Stock
Class of Stock [Line Items]
Shares, outstanding (in shares) | shares	[1]				64,105,000	66,474,000	74,672,000	64,105,000	66,474,000	74,672,000	78,897,000
Common Stock | Subsequent Event
Class of Stock [Line Items]
Reverse stock split conversion ratio		1.03060	1.03060
Common Stock | SL Green Operating Partnership
Class of Stock [Line Items]
Shares, outstanding (in shares) | shares					64,105,276			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.