Investment in Unconsolidated Joint Venture (Condensed Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Rental income	$ 29,769	$ 32,130	$ 58,778	$ 65,608
Other revenue	3,094	4,184	6,465	8,346
Total revenue	39,923	43,677	76,632	85,526
Property operating	10,089	10,098	20,455	21,067
Depreciation and amortization	16,587	22,154	33,812	43,834
Total operating expenses	43,196	47,147	77,120	92,685
Operating income	(3,273)	(3,470)	(488)	(7,159)
Interest expense	(9,312)	(6,347)	(19,038)	(12,596)
Net income	(11,807)	(9,239)	(11,388)	(18,016)
Net loss attributable to stockholders	(11,540)	(8,982)	(11,053)	(17,498)
Company's share of net loss from Worldwide Plaza			1,845	805
Income from unconsolidated joint venture	757	570	1,845	805
Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Rental income	31,120	30,751	62,609	61,265
Other revenue	1,230	1,232	2,460	2,449
Total revenue	32,350	31,983	65,069	63,714
Property operating	11,624	11,727	23,610	23,967
Depreciation and amortization	6,847	6,864	13,619	13,714
Total operating expenses	18,471	18,591	37,229	37,681
Operating income	13,879	13,392	27,840	26,033
Interest expense	(10,255)	(9,992)	(20,509)	(19,874)
Net income	3,624	3,400	7,331	6,159
Company's preferred return	(3,987)	(3,894)	(8,054)	(7,745)
Net loss attributable to stockholders	(363)	(494)	(723)	(1,586)
Company's preferred return	3,987	3,894	8,054	7,745
Company's share of net loss from Worldwide Plaza	(177)	(242)	(353)	(776)
Amortization of basis difference	$ (3,053)	$ (3,082)	$ (5,856)	$ (6,164)