Investment in Unconsolidated Joint Venture (Condensed Income Statement) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Equity Method Investments [Line Items]
Rental income	$ 29,009	$ 33,478
Other revenue	3,371	4,162
Total revenue	36,709	41,849
Property operating	10,366	10,969
Depreciation and amortization	17,225	21,680
Total operating expenses	33,924	45,538
Operating income	2,785	(3,689)
Interest expense	(9,726)	(6,249)
Net income (loss)	419	(8,777)
Net income (loss) attributable to stockholders	487	(8,516)
Company's share of net loss from Worldwide Plaza	1,088	235
Income from unconsolidated joint venture	1,088	235
Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Rental income	31,489	30,514
Other revenue	1,230	1,217
Total revenue	32,719	31,731
Property operating	11,986	12,241
Depreciation and amortization	6,772	6,850
Total operating expenses	18,758	19,091
Operating income	13,961	12,640
Interest expense	(10,254)	(9,882)
Net income (loss)	3,707	2,758
Company's preferred return	(4,067)	(3,851)
Net income (loss) attributable to stockholders	(360)	(1,093)
Company's preferred return	4,067	3,851
Company's share of net loss from Worldwide Plaza	(176)	(534)
Amortization of basis difference	$ (2,803)	$ (3,082)