Segment Information - Schedule of Segment's Contribution to Consolidated Revenues and Net Operating Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 97,377	$ 97,767	$ 95,431	$ 93,431	$ 92,813	$ 96,461	$ 95,026	$ 93,512	$ 384,006	$ 377,812	$ 362,737
Other									1,209	992	872
Consolidated property net operating income									217,441	213,861	206,604
Interest income									168	135	77
Depreciation									(87,458)	(84,759)	(85,608)
Interest expense									(31,587)	(40,286)	(44,704)
Amortization of deferred financing costs									(1,747)	(2,282)	(2,573)
General and administrative									(18,558)	(17,898)	(17,245)
Investment and development									(616)	(2,366)	(1,755)
Other investment costs									(519)	(768)	(1,324)
Severance, impairment and other										(2,266)	(2,417)
Equity in income of unconsolidated real estate entities, net									2,208	1,788	2,090
Net gains on condominium sales activities										2,545	27,944
Other income (expense), net									(1,026)	19	(839)
Net loss on extinguishment of indebtedness									(197)	(18,357)
Income from continuing operations, before gains on sales of real estate assets									79,318	50,358	81,122
Gains on sales of real estate assets, net									1,475	187,825
Income from discontinued operations											29,798
Net income	$ 20,967	$ 20,190	$ 19,651	$ 19,985	$ 19,504	$ 156,435	$ 47,991	$ 14,253	80,793	238,183	110,920
Fully Stabilized Communities [Member]
Segment Reporting Information [Line Items]
Revenues									338,130	329,036	315,518
Consolidated property net operating income									206,325	201,962	194,488
Newly Stabilized Communities [Member]
Segment Reporting Information [Line Items]
Revenues									17,195	11,267	2,587
Consolidated property net operating income									10,519	6,412	616
Lease Up Communities [Member]
Segment Reporting Information [Line Items]
Revenues									5,283	1,745
Consolidated property net operating income									2,142	241	(7)
Held For Sale And Sold Communities [Member]
Segment Reporting Information [Line Items]
Revenues										14,168	23,025
Consolidated property net operating income										7,157	12,725
Other Property Segments, Including Corporate Management Expenses [Member]
Segment Reporting Information [Line Items]
Revenues									22,189	20,604	20,735
Consolidated property net operating income									$ (1,545)	$ (1,911)	$ (1,218)