Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Total interest costs incurred			$ 96,903	$ 92,520
Interest capitalized			(14,787)	(18,568)
Interest expense	$ 28,166	$ 26,287	82,116	73,952
Cash paid for interest, net of amounts capitalized			85,614	70,486
Cash paid for income taxes			699	342
Mortgage loan refinanced			0	166,823
Mortgage loans assumed with acquisition			0	79,401
DownREIT operating partnership units issued with acquisition of noncontrolling interest			0	5,918
DownREIT operating partnership units redeemed for common shares			101	2,569
Shares issued under dividend reinvestment plan			$ 1,431	$ 1,528