Related Party Transactions (Details) (USD $)			3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Alliance Building Services	Jun. 30, 2010 Alliance Building Services	Jun. 30, 2011 Alliance Building Services	Jun. 30, 2010 Alliance Building Services	Jun. 30, 2011 Nancy Peck and Company SquareFoot	Jun. 30, 2011 Entity with Stephen L Green ownership interest	Jun. 30, 2010 Entity with Stephen L Green ownership interest	Jun. 30, 2011 Entity with Stephen L Green ownership interest	Jun. 30, 2010 Entity with Stephen L Green ownership interest
Related Party Transactions
Profit participation from related party			$ 1,000,000	$ 500,000	$ 1,100,000	$ 1,000,000
Payments made for services			3,500,000	3,100,000	6,600,000	6,200,000
Space at 420 Lexington Avenue leased (in square foot)							1,003
Lease rent due per year							35,516
Property management fees from related party								111,000	94,000	221,000	202,000
Amounts due from related parties
Due from joint ventures	423,000	1,062,000
Other	2,156,000	5,233,000
Related party receivables	$ 2,579,000	$ 6,295,000