Stockholders' Equity of the Company (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic Earnings:
Net income attributable to SL Green common stockholders	$ 37,120	$ 37,025	$ 8,276	$ 18,909	$ 19,956	$ 7,732	$ 103,040	$ 25,256	$ 101,330	$ 155,984	$ 617,232
Effect of Dilutive Securities:
Redemption of units to common shares									0	0	0
Diluted Earnings:
Income attributable to SLGOP common unitholders									104,353	161,581	631,861
Basic Shares:
Basic weighted average common shares outstanding (in shares)									92,269,000	89,319,000	83,762,000
Effect of Dilutive Securities:
Redemption of units to common shares (shares)									2,735,000	3,207,000	1,985,000
Stock-based compensation plans (in shares)									262,000	347,000	497,000
Diluted weighted average common stock outstanding (shares)									95,266,000	92,873,000	86,244,000
Common stock shares excluded from the diluted shares outstanding									964,789	627,000	680,000
3.0% exchangeable senior debentures due 2017
Effect of Dilutive Securities:
Stock-based compensation plans (in shares)									0	0	0
Interest rate (as a percent)	3.00%								3.00%
3.0% exchangeable senior debentures due 2027
Effect of Dilutive Securities:
Stock-based compensation plans (in shares)									0	0	0
Interest rate (as a percent)	3.00%								3.00%
4.0% exchangeable senior debentures due 2025
Effect of Dilutive Securities:
Stock-based compensation plans (in shares)									0	0	0
Interest rate (as a percent)	4.00%								4.00%
Common Stock
Effect of Dilutive Securities:
Redemption of units to common shares									3,023	5,597	14,629
Stock options
Effect of Dilutive Securities:
Redemption of units to common shares									$ 0	$ 0	$ 0