Variable Interest Entities ("VIEs") (Details) $ in Thousands	Sep. 30, 2015 USD ($) Entities	Dec. 31, 2014 USD ($) Entities
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number Of Variable Interest Entities	0	0
Non Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Number Of Variable Interest Entities	4	4
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 | $	$ 302,649