Summary of Discontinued Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Units in Real Estate Property	48,343		48,343
Rental revenues	$ 125,522	$ 113,015	$ 366,191	$ 323,223
Other Real Estate Revenue	10,772	9,966	31,596	29,084
Total operating revenues	136,440	123,190	398,252	352,994
Operating Costs and Expenses	89,153	82,268	258,273	235,765
Interest expense	14,941	14,530	45,715	42,428
(Loss) income from discontinued operations before gain on sale	650	753	3,439	4,206
Net loss on insurance and other settlement proceeds on discontinued operations	(1)	99	(5)	43
Gain on sale of discontinued operations	28,788	16,092	71,909	38,474
Income from discontinued operations	29,437	16,944	75,343	42,723
Fountain Lake [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Units in Real Estate Property	113		113
Disposal Groups, Including Discontinued Operations, Name [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental revenues	1,386	5,108	9,084	19,659
Other Real Estate Revenue	119	449	709	1,834
Total operating revenues	1,505	5,557	9,793	21,493
Operating Costs and Expenses	680	3,073	4,147	10,702
Depreciation	110	1,421	1,856	5,401
Interest expense	65	310	351	1,184
Total expense	$ 855	$ 4,804	$ 6,354	$ 17,287