Summary Of Significant Accounting Policies (Supplemental Cash Flow Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Total interest costs incurred	$ 129,001	$ 125,684	$ 113,016
Interest capitalized	18,847	25,559	18,022
Interest expense	110,154	100,125	94,994
Cash paid for interest, net of amounts capitalized	107,494	105,201	90,185
Cash paid for income taxes	675	352	296
NON-CASH INVESTING AND FINANCING TRANSACTIONS (1):
Mortgage loans refinanced	0	166,823	0
Mortgage loans assumed with acquisition	0	79,401	34,385
DownREIT operating partnership units issued with acquisition	0	5,918	0
DownREIT operating partnership units redeemed for common shares	101	2,569	18,679
Shares issued under dividend reinvestment plan	1,884	2,017	2,017
Contribution of noncontrolling interest	$ 1,435	$ 0	$ 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