Partners' Capital of the Operating Partnership (EPS) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Stockholders' Equity
Weighted average common shares outstanding (shares)	100,643,000	100,051,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,025,419	1,349,019
SL Green Operating Partnership
Stockholders' Equity
Net income attributable to SLGOP common unitholders	$ 11,827	$ 24,143
Weighted average common shares outstanding (shares)	105,250,000	104,025,000
Stock-based compensation plans (shares)	304,000	234,000
Diluted weighted average common units outstanding (shares)	105,554,000	104,259,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,025,419	1,349,019