Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stockholders' Equity
Income attributable to SL Green common stockholders	$ 234,946	$ 269,132	$ 503,104
Weighted average common shares outstanding (shares)	100,185,000	99,345,000	95,774,000
Common stock shares excluded from the diluted shares outstanding (shares)	774,782	263,991	737,361
SL Green Operating Partnership
Stockholders' Equity
Net Income (Loss) Allocated to, Common Unitholders	$ 245,082	$ 279,697	$ 521,571
Weighted average common shares outstanding (shares)	104,508,000	103,244,000	99,288,000
Stock-based compensation plans (shares)	373,000	490,000	408,000
Diluted weighted average common units outstanding (shares)	104,881,000	103,734,000	99,696,000
Common stock shares excluded from the diluted shares outstanding (shares)	774,782	263,991	737,361