Stockholders' Equity (Details 5) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Basic Earnings:
Net income attributable to SL Green common stockholders	$ 18,909	$ 25,256
Effect of Dilutive Securities:
Redemption of units to common shares	555	888
Diluted Earnings:
Income attributable to SL Green common stockholders	$ 19,464	$ 26,144
Basic Shares:
Basic weighted average common shares outstanding (in shares)	91,399,000	86,744,000
Effect of Dilutive Securities:
Redemption of units to common shares	2,687,000	3,049,000
Stock-based compensation plans (in shares)	216,000	380,000
Diluted Shares	94,302,000	90,173,000
Common stock shares excluded from the diluted shares outstanding	988,887	785,929
3.0% exchangeable senior debentures due 2017
Effect of Dilutive Securities:
Interest rate (as a percent)	3.00%
3.0% exchangeable senior debentures due 2027
Effect of Dilutive Securities:
Interest rate (as a percent)	3.00%
4.0% exchangeable senior debentures due 2025
Effect of Dilutive Securities:
Interest rate (as a percent)	4.00%