Fair Value Disclosures - Financial Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial paper, maturity	90
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 23,575	$ 23,825
Restricted cash	9,889	13,383
Mortgage notes payable, net	333,853	418,052
Lines of credit	215,000	105,000
Notes payable, net	743,475	743,181
Carrying Value | 2445 M Street Note Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
2445 M Street note receivable	3,884	3,849
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	23,575	23,825
Restricted cash	9,889	13,383
Mortgage notes payable, net	342,496	426,693
Lines of credit	215,000	105,000
Notes payable, net	777,755	753,816
Fair Value | 2445 M Street Note Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
2445 M Street note receivable	$ 3,897	$ 4,275