Accumulated Other Comprehensive Loss of the Company (Details) (USD $)			9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 SL Green Realty Corp	Sep. 30, 2014 SL Green Realty Corp Net unrealized loss on derivative instruments		Sep. 30, 2014 SL Green Realty Corp Unrealized gains and loss on marketable securities	Sep. 30, 2014 SL Green Realty Corp Joint Venture Net unrealized loss on derivative instruments
Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward]
December 31, 2013	$ (2,896,000)	$ (15,211,000)	$ (15,211,000)	$ (15,125,000)	[1]	$ 4,784,000	$ (4,870,000)	[2]
Other comprehensive income before reclassifications			6,851,000	1,293,000	[1]	1,209,000	4,349,000	[2]
Amounts reclassified from accumulated other comprehensive income			5,464,000	3,658,000	[1]	0	1,806,000	[2]
September 30, 2014	(2,896,000)	(15,211,000)	(2,896,000)	(10,174,000)	[1]	5,993,000	1,285,000	[2]
Deferred net losses from terminated hedges	$ 12,200,000	$ 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 September 30, 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 $12.2 million and $13.8 million, respectively.

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