Related Party Transactions (Details Textual) (USD $) In Thousands, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended		2 Months Ended	1 Months Ended			3 Months Ended	6 Months Ended		1 Months Ended
	Mar. 15, 2013	Jun. 30, 2013 sqft	Jun. 30, 2012	Jun. 30, 2013 sqft	Jun. 30, 2012	Jun. 25, 2012 Slg Graybar Sublease Llc [Member] sqft	May 31, 2005 Slg Graybar Sublease Llc [Member] sqft	Jun. 30, 2009 Slg Graybar Sublease Llc [Member] sqft	May 31, 2005 Slg Graybar Sublease Llc [Member] Minimum [Member]	May 31, 2005 Slg Graybar Sublease Llc [Member] Maximum [Member]	Jan. 31, 2013 Sl Green [Member]	Jun. 30, 2013 Sl Green [Member]	Jun. 30, 2013 Sl Green [Member]	Dec. 31, 2012 Sl Green [Member]	Jun. 30, 2013 Fifth Fee Owner Llc [Member] sqft	Jun. 30, 2013 Fifth Fee Owner Llc [Member] Minimum [Member]	Jun. 30, 2013 Fifth Fee Owner Llc [Member] Maximum [Member]
Business Acquisition Area of Land		1,600,000		1,600,000		600	7,300	2,260							6,580
Lease Term							10 years								10 years
Additional Rent Carried For Initial Lease Year								$ 103
Additional Rent Carried For Final Lease Year								123
Rent Reduced For Initial Lease Year						29
Rent Reduced For Final Lease Year						38
Operating Leases, Rent Expense, Net		96	77	191	173				249	315						373	463
Equity Method Investment, Ownership Percentage														10.60%
Carrying Value Of Interest In Joint Venture														7,215
Net gains from disposals	389,140	0	53	389,140	11,996							0	458
Sale Of Joint Venture Interest											10.60%
Proceeds from sale of joint venture to related party				8,275	0						8,275
Net realized gain on sale of joint venture investment											$ 1,317