Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended						3 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Series G Preferred Units	Dec. 31, 2013 Series G Preferred Units	Mar. 31, 2014 Series H Preferred Units	Dec. 31, 2013 Series H Preferred Units	Mar. 31, 2014 SL Green Operating Partnership	Dec. 31, 2013 SL Green Operating Partnership	Jan. 31, 2012 SL Green Operating Partnership Series G Preferred Units	Nov. 30, 2011 SL Green Operating Partnership Series H Preferred Units	Nov. 30, 2011 SL Green Operating Partnership Series E preferred units	Nov. 30, 2011 SL Green Operating Partnership Series F Preferred Units
Organization
Noncontrolling interest in the operating partnership (as a percent)							3.05%	2.96%
Number of units of operating partnership owned by the noncontrolling interest unit holders (shares)							3,000,257	2,902,317
Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares)							3,000,257
Number of preferred units issued (in shares)			1,902,000	1,902,000	80,000	80,000			1,902,000	80,000	22,658	60
Dividend rate preferred units (as a percent)									4.50%	6.00%	5.00%
Liquidation preference of preferred units (in dollars per share)			$ 25.00	$ 25.00	$ 25.00	$ 25.00			$ 25.00	$ 25.00
Annual dividends on preferred units (in dollars per share)									$ 1.125	$ 1.50	$ 1.00	$ 1,000
Operating partnership common stock value use for conversion of preferred units (in dollars per share)									$ 88.50
Number of company common stock issue on redemption of operation partnership common units									1
Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership
Balance at beginning of period	$ 265,476						$ 265,476	$ 212,907
Distributions	(1,586)						(1,500)	(4,146)
Issuance of common units	517						17,314	24,750
Redemption of common units							(16,583)	(17,287)
Net income	4,729	555					4,729	3,023
Accumulated other comprehensive (loss) income allocation	(42)	59					(42)	611
Fair value adjustment							29,464	45,618
Balance at end of period	$ 298,858						$ 298,858	$ 265,476