Partners' Capital of the Operating Partnership - EPS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stockholders' Equity
Income attributable to SL Green common stockholders	$ 163,658	$ 64,688	$ 167,829	$ 446,319
Weighted average common shares outstanding (shares)	99,621,000	95,734,000	99,205,000	95,437,000
Common stock shares excluded from the diluted shares outstanding (shares)	263,236	231,970	233,586	769,790
SL Green Operating Partnership
Stockholders' Equity
Income attributable to SL Green common stockholders	$ 170,125	$ 67,324	$ 174,463	$ 462,329
Weighted average common shares outstanding (shares)	103,522,000	99,319,000	103,129,000	98,860,000
Stock-based compensation plans (shares)	407,000	387,000	480,000	462,000
Diluted weighted average common units outstanding (shares)	103,929,000	99,706,000	103,609,000	99,322,000
Common stock shares excluded from the diluted shares outstanding (shares)	263,236	231,970	233,586	769,790