Assets for Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 2,527,410	$ 2,530,468
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,132,487	1,017,015
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	668,910	668,109
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	639,969	760,132
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 86,044	$ 85,212