Organization and Basis of Presentation - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($) ft² building shares	Dec. 31, 2022
Organization
Number of buildings | building	51
Unaudited Approximate Usable Square Feet | ft²	29,708,910
Debt and preferred equity investments including investments held by unconsolidated joint ventures | $	$ 334.3
Debt and preferred equity investments and other financing receivables included in other balance sheet items | $	$ 8.3
Number of shares to be received on redemption of one unit of limited partnership interests (shares) | shares	1
Managed office properties
Organization
Number of buildings | building	1
Unaudited Approximate Usable Square Feet | ft²	300,000
Service Corporation
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	95.00%
Operating Partnership | SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	6.04%	5.39%
SL Green Management | SL Green Management LLC
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%