Accumulated Other Comprehensive Loss of the Operating Partnership (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) of the Operating Partnership [Roll Forward]
December 31, 2013			$ (15,211,000)
March 31, 2014	(14,872,000)		(15,211,000)
Deferred net losses from terminated hedges	13,300,000		13,800,000
SL Green Operating Partnership
Accumulated Other Comprehensive Income (Loss) of the Operating Partnership [Roll Forward]
December 31, 2013	(15,662,000)
Other comprehensive income (loss) before reclassifications	(1,668,000)
Amounts reclassified from accumulated other comprehensive income	1,965,000
March 31, 2014	(15,365,000)
Deferred net losses from terminated hedges	13,700,000		14,200,000
Unrealized gains and loss on marketable securities | SL Green Operating Partnership
Accumulated Other Comprehensive Income (Loss) of the Operating Partnership [Roll Forward]
December 31, 2013	(15,573,000)	[1]
Other comprehensive income (loss) before reclassifications	(51,000)	[1]
Amounts reclassified from accumulated other comprehensive income	692,000	[1]
March 31, 2014	(14,932,000)	[1]
Unrealized gains and loss on marketable securities | SL Green Operating Partnership
Accumulated Other Comprehensive Income (Loss) of the Operating Partnership [Roll Forward]
December 31, 2013	4,926,000
Other comprehensive income (loss) before reclassifications	129,000
Amounts reclassified from accumulated other comprehensive income	0
March 31, 2014	5,055,000
Joint Venture | Unrealized gains and loss on marketable securities | SL Green Operating Partnership
Accumulated Other Comprehensive Income (Loss) of the Operating Partnership [Roll Forward]
December 31, 2013	(5,015,000)	[2]
Other comprehensive income (loss) before reclassifications	(1,746,000)	[2]
Amounts reclassified from accumulated other comprehensive income	1,273,000	[2]
March 31, 2014	$ (5,488,000)	[2]

[1] Amount reclassified from accumulated other comprehensive income (loss) are included in interest expense in the respective consolidated statements of income. As of March 31, 2014 and December 31, 2013, the deferred net losses from these terminated hedges, which are included in accumulated other comprehensive loss relating to net unrealized loss on derivative instrument, were $13.7 million and $14.2 million, respectively.

[2] Amounts reclassified from accumulated other comprehensive income (loss) are included in equity in net income from unconsolidated joint ventures in the respective consolidated statements of income.