Capital (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended						3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Aug. 31, 2012 Series I Preferred Units	Mar. 31, 2013 Series I Preferred Units	Sep. 30, 2012 Series C preferred units	Mar. 31, 2013 Series C preferred units	Jul. 31, 2012 Series D preferred units	Mar. 31, 2013 Series E preferred units	Nov. 30, 2011 Series H Preferred Units	Jan. 31, 2012 Series G Preferred Units	Mar. 31, 2013 Series F Preferred Units	Mar. 31, 2013 At-the-market equity offering program	Jul. 31, 2011 At-the-market equity offering program	Mar. 31, 2013 SL Green	Mar. 31, 2013 SL Green Dividend Reinvestment and Stock Purchase Plan (DRIP)	Mar. 31, 2012 SL Green Dividend Reinvestment and Stock Purchase Plan (DRIP)
Capital
Number of common units held by parent														91,555,082
Period for which redemption right of unitholder is restricted	1 year
Number of shares to be received on redemption of one unit of limited partnership interests	1
Aggregate value of the shares of common stock to be sold													$ 250,000,000
Aggregate value of common stock remained available for issuance												45,400,000
Limited partnership interest held by noncontrolling investors (as a percent)	2.75%
Number of units owned by other limited partners	2,585,675
Number of shares reserved for conversion of units owned by other limited partners	2,602,342
Preferred stock, shares outstanding				9,200,000	11,700,000	7,700,000		22,658			60
Number of preferred units issued (in shares)									80,000	1,902,000
Preferred stock, dividend rate (as a percent)				6.50%		7.625%	7.875%	5.00%	6.00%	4.50%
Net proceeds from the offerings contributed by SL Green			221,900,000
Preferred stock, liquidation preference (in dollars per share)				$ 25.00		$ 25.00	$ 25.00	$ 1.00	$ 25.00	$ 25.00	$ 1,000.00
Preferred stock, annual distributions per share (in dollars per share)				$ 1.625		$ 1.90625	$ 1.96875		$ 1.50	$ 1.125
Conversion ratio, denominator (in dollars per unit)										$ 88.50
Common stock, shares authorized																3,500,000
Number of shares redeemed					4,000,000		4,000,000
Redemption price (in dollars per share)					$ 25.00		$ 25.00
Cumulative and unpaid dividend (in dollars per share)					$ 0.3707		$ 0.4922
Preferred unit redemption costs					6,300,000		3,700,000
Number of common partnership units exchanged (in shares)															170	1,300,000
Proceeds from shares sold	$ (57,000)	$ 122,953,000													$ 13,000	$ 99,500,000