Investment in Unconsolidated Joint Venture (Condensed Balance Sheet) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Oct. 30, 2013
Schedule of Equity Method Investments [Line Items]
Real estate assets, at cost	$ 1,828,611	$ 1,822,903
Less accumulated depreciation and amortization	(189,856)	(172,668)
Total real estate investments, net	1,638,755	1,650,235
Cash and cash equivalents	100,162	98,604	$ 49,360	$ 22,512
Total assets	2,019,895	2,064,762
Total liabilities	954,003	972,493
Deficit	(387,670)	(369,273)
Total liabilities and equity	2,019,895	2,064,762
Company's basis	208,558	215,370
Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Real estate assets, at cost	714,654	714,642
Less accumulated depreciation and amortization	(122,077)	(117,092)
Total real estate investments, net	592,577	597,550
Cash and cash equivalents	4,689	9,036
Other assets	267,125	259,894
Total assets	864,391	866,480
Debt	875,000	875,000			$ 875,000
Other liabilities	17,619	15,515
Total liabilities	892,619	890,515
Deficit	(28,228)	(24,035)
Total liabilities and equity	864,391	866,480
Company's basis	$ 208,558	$ 215,370