Stockholders' Equity of the Company (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Basic Earnings:
Income attributable to SL Green common stockholders	$ 163,658	$ 64,688	$ 167,829	$ 446,319
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 170,126	$ 67,324	$ 174,463	$ 462,329
Basic Shares:
Weighted average common shares outstanding (shares)	99,621,000	95,734,000	99,205,000	95,437,000
Effect of Dilutive Securities:
Redemption of units to common shares (shares)	3,901,000	3,585,000	3,924,000	3,423,000
Stock-based compensation plans (shares)	407,000	387,000	480,000	462,000
Diluted weighted average common stock 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
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 6,468	$ 2,636	$ 6,634	$ 16,010