Consolidated Statements of Cash Flows (Parenthetical) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly distributions declared, per share/unit (usd per share/unit)	$ 0.60	$ 0.50	$ 0.33
SL Green Operating Partnership
Quarterly distributions declared, per share/unit (usd per share/unit)	$ 0.60	$ 0.50	$ 0.33

Common Stock, Dividends, Per Share, Quarterly Distributions

No definition available.

Name:	slg_CommonStockDividendsPerShareQuarterlyDistributions
Namespace Prefix:	slg_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration