Organization and Basis of Presentation - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
SL Green Operating Partnership | Service Corporation
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	95.00%
SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	5.03%	4.70%
SLG Management LLC | SL Green Management
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%