Partners' Capital of the Operating Partnership (EPS) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stockholders' Equity
Weighted average common shares outstanding (shares)	100,233,000	99,621,000	100,140,000	99,205,000
Common stock shares excluded from the diluted shares outstanding (shares)	673,298	263,236	753,344	231,970
SL Green Operating Partnership
Stockholders' Equity
Net income attributable to SLGOP common unitholders	$ 35,915	$ 170,125	$ 199,101	$ 174,463
Weighted average common shares outstanding (shares)	104,730,000	103,522,000	104,412,000	103,129,000
Stock-based compensation plans (shares)	413,000	407,000	349,000	480,000
Diluted weighted average common units outstanding (shares)	105,143,000	103,929,000	104,761,000	103,609,000
Common stock shares excluded from the diluted shares outstanding (shares)	673,298	753,344	263,236	231,970