Accumulated Other Comprehensive Loss of the Company (Details) (USD $)			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 SL Green Realty Corp	Mar. 31, 2014 SL Green Realty Corp Unrealized gains and loss on marketable securities		Mar. 31, 2014 SL Green Realty Corp Unrealized gains and loss on marketable securities	Mar. 31, 2014 SL Green Realty Corp Joint Venture Unrealized gains and loss on marketable securities
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
December 31, 2013	$ (14,872,000)	$ (15,211,000)	$ (15,211,000)	$ (15,125,000)	[1]	$ 4,784,000	$ (4,870,000)	[2]
Other comprehensive income (loss) before reclassifications			(1,563,000)	2,000	[1]	109,000	(1,674,000)	[2]
Amounts reclassified from accumulated other comprehensive income			1,902,000	670,000	[1]	0	1,232,000	[2]
March 31, 2014	(14,872,000)	(15,211,000)	(14,872,000)	(14,453,000)	[1]	4,893,000	(5,312,000)	[2]
Deferred net losses from terminated hedges	$ 13,300,000	$ 13,800,000

[1] Amounts 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 $13.3 million and $13.8 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.