Investments in Unconsolidated Real Estate Entities - Summary of Financial Information for Apartment LLCs (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Real Estate Properties [Line Items]
Real estate assets, net of accumulated depreciation of $52,012 and $49,153 at June 30, 2015 and December 31, 2014, respectively	$ 2,151,111	$ 2,128,767
Total assets	2,314,032	2,311,798
Total liabilities	1,027,241	1,018,752
Members' equity	1,280,236	1,285,960	$ 1,173,934	$ 1,152,731
Total liabilities and members' equity	2,314,032	2,311,798
Unconsolidated Properties [Member]
Real Estate Properties [Line Items]
Real estate assets, net of accumulated depreciation of $52,012 and $49,153 at June 30, 2015 and December 31, 2014, respectively	207,785	208,493
Cash and other	7,261	5,490
Total assets	215,046	213,983
Mortgage notes payable	177,723	177,723
Other liabilities	4,721	3,445
Total liabilities	182,444	181,168
Members' equity	32,602	32,815
Total liabilities and members' equity	215,046	213,983
Company's equity investment in Apartment LLCs	$ (12,480)	$ (12,565)