Investment in Unconsolidated Joint Venture - Condensed Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Schedule of Equity Method Investments [Line Items]
Rental income	$ 32,531	$ 27,171
Other revenue	4,162	3,516
Total revenues	40,902	33,592
Property operating	10,969	8,858
Depreciation and amortization	20,732	21,013
Total operating expenses	44,590	36,448
Operating income	(3,688)	(2,856)
Interest expense	(5,933)	(3,939)
Net loss	(8,460)	(8,155)
Net loss attributable to stockholders	(8,199)	(8,156)
Company's share of net loss from Worldwide Plaza	235	(1,984)
Income (loss) from unconsolidated joint venture	235	(1,984)
Worldwide Plaza
Schedule of Equity Method Investments [Line Items]
Rental income	30,514	27,655
Other revenue	1,217	1,215
Total revenues	31,731	28,870
Property operating	12,241	11,513
Depreciation and amortization	6,850	6,368
Total operating expenses	19,091	17,881
Operating income	12,640	10,989
Interest expense	(9,882)	(9,882)
Net loss	2,758	1,107
Company's preferred distribution	(3,851)	(3,851)
Joint venture partner distributions	0	(2,560)
Net loss attributable to stockholders	(1,093)	(5,304)
Company's preferred distribution	(3,851)	(3,851)
Company's share of net loss from Worldwide Plaza	(534)	(2,594)
Amortization of difference in basis	(3,082)	(3,241)
Income (loss) from unconsolidated joint venture	$ 235	$ (1,984)