Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity
Income attributable to SL Green common stockholders	$ 269,132	$ 503,104	$ 101,330
Weighted average common shares outstanding (shares)	99,345,000	95,774,000	92,269,000
Common stock shares excluded from the diluted shares outstanding (shares)	263,991	737,361	964,789
SL Green Operating Partnership
Stockholders' Equity
Income attributable to SL Green common stockholders	$ 279,697	$ 521,571	$ 104,353
Weighted average common shares outstanding (shares)	103,244,000	99,288,000	95,004,000
Stock-based compensation plans (shares)	490,000	408,000	262,000
Diluted weighted average common units outstanding (shares)	103,734,000	99,696,000	95,266,000
Common stock shares excluded from the diluted shares outstanding (shares)	263,991	737,361	964,789