Stockholders' Equity of the Company (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic Earnings:
Net income attributable to SL Green common stockholders	$ 56,787	$ 64,688	$ 235,539	$ 146,090	$ 37,120	$ 37,025	$ 8,276	$ 18,909	$ 503,104	$ 101,330	$ 155,984
Diluted Earnings:
Income attributable to SLGOP common unitholders									521,571	104,353	161,581
Basic Shares:
Basic weighted average common shares outstanding (in shares)									95,774,000	92,269,000	89,319,000
Effect of Dilutive Securities:
Redemption of units to common shares (shares)									3,514,000	2,735,000	3,207,000
Stock-based compensation plans (in shares)									408,000	262,000	347,000
Diluted weighted average common stock outstanding (shares)									99,696,000	95,266,000	92,873,000
Common stock shares excluded from the diluted shares outstanding									737,361	964,789	627,000
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares									$ 18,467	$ 3,023	$ 5,597