Investment in Unconsolidated Joint Venture (Details) - USD ($)	Oct. 30, 2013	Jun. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint venture		$ 226,306,000	$ 225,501,000
Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Ownership percentage	48.90%
Aggregate cost	$ 220,100,000
Agreed upon value	1,325,000,000
Notes payable	$ 875,000,000	875,000,000	875,000,000
Interest rate	4.60%
Purchase obligation	$ 1,400,000,000
Purchase option term	38 months
Fee for non-exercise of purchase option		25,000,000
Difference between carrying amount and underlying equity	$ 260,600,000
Investments in unconsolidated joint venture		226,306,000	$ 225,501,000
Parent Company | Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Notes payable		$ 427,900,000