Investments in Unconsolidated Real Estate Entities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2014 Property	Dec. 31, 2013	Sep. 30, 2014 3.50% Mortgage Note Payable [Member]	Sep. 30, 2014 5.63% Mortgage Notes Payable [Member]	Sep. 30, 2014 5.71% Mortgage Notes Payable [Member]	Sep. 30, 2014 Unconsolidated Properties [Member] Property	Dec. 31, 2013 Unconsolidated Properties [Member]	Sep. 30, 2014 Washington, D.C. [Member] Unconsolidated Properties [Member] Property	Sep. 30, 2014 Atlanta, Georgia [Member] Unconsolidated Properties [Member] Property	Sep. 30, 2014 Minimum [Member] Unconsolidated Properties [Member]	Sep. 30, 2014 Maximum [Member] Unconsolidated Properties [Member]
Equity method investment, ownership percentage										25.00%	35.00%
Number of real estate properties	58					4		1	3
Investment in owned subsidiaries	$ 4,095	$ 4,056
Investments in unconsolidated real estate entities	16,654	16,687				16,654	16,687
Mortgage note payable			$ 51,000	$ 85,724	$ 41,000	$ 177,723	$ 177,723
Mortgage notes payable bearing interest rate			3.50%	5.63%	5.71%
Mortgage note payable maturity date			2019	2017	January 2018
Automatic extension period (in years)					1 year