Related Party Transactions (Details) (USD $)			3 Months Ended					3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Alliance Building Services	Mar. 31, 2012 Alliance Building Services	Mar. 31, 2013 A-List Marketing, LLC	Mar. 31, 2012 A-List Marketing, LLC	Mar. 31, 2013 Nancy Peck and Company sqft	Mar. 31, 2013 Entity with Stephen L Green ownership interest	Mar. 31, 2012 Entity with Stephen L Green ownership interest
Related Party Transactions
Profit participation from related party			$ 1,000,000	$ 800,000
Payments made for services			4,100,000	3,500,000	2,400	11,700
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								118,200	89,000
Amounts due from/to related parties
Due from joint ventures	4,032,000	511,000
Other	7,137,000	7,020,000
Related party receivables	11,169,000	7,531,000
Due to joint venture (included in Accounts payable and accrued expenses)		$ (8,401,000)