Summary Of Significant Accounting Policies (Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Total interest costs incurred	$ 130,110	$ 129,001	$ 125,684
Interest capitalized	20,487	18,847	25,559
Interest expense	109,623	110,154	100,125
Cash paid for interest, net of amounts capitalized	106,180	107,494	105,201
Cash paid for income taxes	483	675	352
NON-CASH INVESTING AND FINANCING TRANSACTIONS (1):
Mortgage loans refinanced	0	0	166,823
Mortgage loans assumed with acquisition	98,041	0	79,401
DownREIT operating partnership units issued with acquisition	0	0	5,918
DownREIT operating partnership units redeemed for common shares	14,105	101	2,569
Settlement of partner loan via dilution	5,379	0	0
Shares issued under dividend reinvestment plan	1,784	1,884	2,017
Contribution of noncontrolling interest	$ 0	$ 1,435	$ 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