Organization and Basis of Presentation - Narrative (Details)	1 Months Ended	12 Months Ended
	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($) ft² building shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Organization
Number of Buildings | building		50
Approximate Square Feet | ft²		29,695,841
Number of shares to be received on redemption of one unit of limited partnership interests (shares) | shares		1
Mortgages and other loans payable, net		$ 1,491,319,000	$ 3,227,563,000
Repayments of mortgages		25,826,000	292,364,000	$ 375,044,000
Due from joint ventures
Organization
Mortgages and other loans payable, net		$ 14,799,277,000	12,348,954,000
2 Herald Square | Due from joint ventures | Subsequent Event
Organization
Consideration transferred	$ 0
Investment in joint venture, ownership percentage	95.00%
Mortgages and other loans payable, net	$ 182,500,000
Repayments of mortgages	7,000,000
717 Fifth Avenue | Due from joint ventures | Subsequent Event
Organization
Gross Asset Valuation	$ 963,000,000
Managed Office Properties
Organization
Approximate Square Feet | ft²		400,000
Debt and preferred equity investments including investments held by unconsolidated joint ventures		$ 346,700,000
Debt and preferred equity investments and other financing receivables included in other balance sheet items		$ 7,900,000
Office
Organization
Number of Buildings | building		1
Retail building
Organization
Number of Buildings | building		1
SL Green Operating Partnership
Organization
Mortgages and other loans payable, net		$ 1,491,319,000	3,227,563,000
Repayments of mortgages		$ 25,826,000	$ 292,364,000	$ 375,044,000
Service Corporation
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)		95.00%
SLG Management LLC | SL Green Management
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)		100.00%
Operating Partnership | SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)		5.75%	5.39%