Stockholders' Equity of the Company (Earnings per Share)(Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic Earnings:
Income attributable to SL Green common stockholders	$ 23,221	$ 43,277
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 24,143	$ 45,020
Basic Shares:
Weighted average common shares outstanding (shares)	100,051,000	98,402,000
Effect of Dilutive Securities:
Operating Partnership units redeemable for common shares (shares)	3,974,000	3,964,000
Stock-based compensation plans (shares)	234,000	653,000
Diluted weighted average common stock outstanding (shares)	104,259,000	103,019,000
Common stock shares excluded from the diluted shares outstanding (shares)	1,349,019	203,975
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares	$ 922	$ 1,743