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, 2014	Dec. 31, 2013	Jun. 30, 2014 Alliance Building Services	Jun. 30, 2013 Alliance Building Services	Jun. 30, 2014 Alliance Building Services	Jun. 30, 2013 Alliance Building Services	Jun. 30, 2014 A-List Marketing, LLC	Jun. 30, 2013 A-List Marketing, LLC	Jun. 30, 2014 A-List Marketing, LLC	Jun. 30, 2013 A-List Marketing, LLC	Jun. 30, 2014 Nancy Peck and Company sqft	Jun. 30, 2014 Entity with Stephen L Green ownership interest	Jun. 30, 2013 Entity with Stephen L Green ownership interest	Jun. 30, 2014 Entity with Stephen L Green ownership interest	Jun. 30, 2013 Entity with Stephen L Green ownership interest
Related Party Transactions
Profit participation from related party			$ 1,000,000	$ 900,000	$ 1,900,000	$ 1,900,000
Related party expenses			4,700,000	4,300,000	8,200,000	8,400,000	77,100	104,900	94,900	107,300
Space at 420 Lexington Avenue leased (sqft)											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												111,600	95,500	216,400	213,700
Amounts due from/to related parties
Due from joint ventures	1,484,000	2,376,000
Other	7,431,000	6,154,000
Related party receivables	$ 8,915,000	$ 8,530,000