Assets for Reportable Segment (Detail) - Parent Company [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 11,532,801	$ 11,604,491
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	4,038,127	4,126,885
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,731,050	1,768,183
Non-Same Store and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	5,527,583	5,479,780
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 236,041	$ 229,643