Commitments and Contingencies Major Customers and Other Concentrations (Details) (Customer Concentration Risk [Member], Sales Revenue, Services, Net [Member])	12 Months Ended
	Dec. 31, 2013 tenant office_and_property	Dec. 31, 2012 tenant office_and_property
Concentration Risk [Line Items]
Number of tenants	3	3
Number of properties	3	3
Empire State Building Co. [Member]
Concentration Risk [Line Items]
Concentration risk percentage	13.01%
One Grand Central Place [Member]
Concentration Risk [Line Items]
Concentration risk percentage	20.99%	24.20%
First Stamford Place [Member]
Concentration Risk [Line Items]
Concentration risk percentage	11.62%	13.93%
250 West 57th Street [Member]
Concentration Risk [Line Items]
Concentration risk percentage		10.44%
Major Tenant Three [Member]
Concentration Risk [Line Items]
Concentration risk percentage	11.41%	10.62%
Customer 1 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	6.01%	4.43%
Customer 2 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	2.72%	3.21%
Customer 3 [Member]
Concentration Risk [Line Items]
Concentration risk percentage	2.68%	2.98%