Assets for Reportable Segment (Detail) (Parent Company [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 6,783,014	$ 6,841,925
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,227,413	1,252,575
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	764,383	796,697
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,637,072	4,638,892
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 154,146	$ 153,761