Assets for Reportable Segment (Detail) - Parent Company [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 6,887,341	$ 6,833,594
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,803,518	1,253,995
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,676,365	1,003,426
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,266,054	4,509,517
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 141,404	$ 66,656