Segment Information (Assets for Reportable Segments) (Details) - Parent Company [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 6,847,781	$ 6,821,778
Large Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,768,455	3,867,457
Secondary Market Same Store
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,661,956	1,708,389
Non Same Store And Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,344,833	1,189,682
Corporate assets
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 72,537	$ 56,250