Related Party Transactions (Details) (USD $)			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Alliance Building Services	Jun. 30, 2011 Alliance Building Services	Jun. 30, 2012 Alliance Building Services	Jun. 30, 2011 Alliance Building Services	Jun. 30, 2012 A-List Marketing, LLC	Jun. 30, 2011 A-List Marketing, LLC	Jun. 30, 2012 A-List Marketing, LLC	Jun. 30, 2011 A-List Marketing, LLC	Jun. 30, 2012 Nancy Peck and Company sqft	Jun. 30, 2012 Entity with Stephen L Green ownership interest	Jun. 30, 2011 Entity with Stephen L Green ownership interest	Jun. 30, 2012 Entity with Stephen L Green ownership interest	Jun. 30, 2011 Entity with Stephen L Green ownership interest
Related Party Transactions
Profit participation from related party			$ 800,000	$ 1,000,000	$ 1,600,000	$ 1,100,000
Payments made for services			4,700,000	3,500,000	8,200,000	6,600,000	44,200	40,700	55,900	66,200
Space at 420 Lexington Avenue leased (in square feet)											1,003
Lease rent due per year											35,516
Increased lease rent due per year beginning in year seven											40,000
Property management fees from related party												110,000	111,000	199,000	221,000
Amounts due from related parties
Due from joint ventures	515,000	477,000
Other	7,278,000	3,524,000
Related party receivables	$ 7,793,000	$ 4,001,000