Stockholders' Equity of the Company (Earnings per Share)(Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic Earnings:
Income attributable to SL Green common stockholders	$ 234,946	$ 269,132	$ 503,104
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 245,082	$ 279,697	$ 521,571
Basic Shares:
Weighted average common shares outstanding (shares)	100,185,000	99,345,000	95,774,000
Effect of Dilutive Securities:
Redemption of units to common shares (shares)	4,323,000	3,899,000	3,514,000
Stock-based compensation plans (shares)	373,000	490,000	408,000
Diluted weighted average common stock outstanding (shares)	104,881,000	103,734,000	99,696,000
Common stock shares excluded from the diluted shares outstanding (shares)	774,782	263,991	737,361
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 10,136	$ 10,565	$ 18,467