Noncontrolling Interests on the Company's Consolidated Financial Statements - Schedule of Common Unit Activity (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Rollforward Analysis of Preferred Unit Activity
Issuance of common and preferred units		$ 4,686	$ 1,823
Redemption of preferred units		(15,631)	(5,674)
SL Green Operating Partnership
Rollforward Analysis of Preferred Unit Activity
Issuance of common and preferred units	$ (61)	4,686	1,823
Redemption of preferred units			(5,674)
SL Green Operating Partnership | Preferred stock
Rollforward Analysis of Preferred Unit Activity
Balance at beginning of period		164,210	$ 166,501	$ 166,501
Issuance of common and preferred units		0		0
Redemption of preferred units		0		(2,503)
Dividends paid on preferred units		(4,299)		(4,453)
Accrued dividends on preferred units		4,308		4,665
Balance at end of period	$ 164,219	$ 164,219		$ 164,210