Stockholders' Equity of the Company (Earnings per Share)(Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic Earnings:
Income attributable to SL Green common stockholders	$ 269,132	$ 503,104	$ 101,330
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 279,697	$ 521,571	$ 104,353
Basic Shares:
Weighted average common shares outstanding (shares)	99,345,000	95,774,000	92,269,000
Effect of Dilutive Securities:
Redemption of units to common shares (shares)	3,899,000	3,514,000	2,735,000
Stock-based compensation plans (shares)	490,000	408,000	262,000
Diluted weighted average common stock 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
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 10,565	$ 18,467	$ 3,023