Assets for Reportable Segment (Detail) (Parent Company [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 6,799,682	$ 6,831,028
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,832,422	1,253,995
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,691,479	1,003,426
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,206,734	4,506,951
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 69,047	$ 66,656