Variable Interest Entities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Consolidated Variable Interest Entities [Member] | Independence Plaza And Warner Building [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net		$ 0
Consolidated Variable Interest Entities [Member] | One Park Avenue, Independence Plaza, Warner Building, Suffolk Downs [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net	$ 0
Non Consolidated Variable Interest Entities [Member] | Independence Plaza And Warner Building [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets		$ 286,783
Non Consolidated Variable Interest Entities [Member] | One Park Avenue, Independence Plaza, Warner Building, Suffolk Downs [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 305,865