Assets for Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 2,834,217	$ 2,751,068
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,272,055	1,108,827
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	809,478	654,315
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	692,655	949,398
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 60,029	$ 38,528