Summary Of Significant Accounting Policies (Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SUPPLEMENTAL DISCLOSURES:
Total interest costs incurred	$ 110,675	$ 114,912	$ 121,158
Interest capitalized	18,122	20,971	16,181
Interest expense	92,553	93,941	104,977
Cash paid for interest, net of amounts capitalized	116,335	100,011	120,934
Cash paid for income taxes	274	278	410
NON-CASH INVESTING AND FINANCING TRANSACTIONS:
Mortgage loans assumed with acquisition	89,516	68,282	0
DownREIT operating partnership units issued with acquisition	7,742	65,348	0
Mortgage loans refinanced	0	64,205	0
Shares issued under dividend reinvestment plan	1,977	1,855	1,779
Repayment of note payable with public funding/related construction-in-progress offset	$ 0	$ 10,000	$ 0
Minimum | Retail and commercial
Operating Leased Assets [Line Items]
Operating lease, term	3 years
Maximum | Retail and commercial
Operating Leased Assets [Line Items]
Operating lease, term	10 years