Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounting Policies [Abstract]
Total interest costs incurred			$ 73,942	$ 64,755
Interest capitalized			(11,424)	(9,240)
Interest expense	$ 34,073	$ 27,482	62,518	55,515
Cash paid for interest, net of amounts capitalized			52,715	53,588
Cash paid for income taxes			428	419
DownREIT operating partnership units issued with acquisition			18,920	0
Mortgage loans assumed with acquisition			8,903	0
DownREIT operating partnership units redeemed for common shares			0	11,935
Shares issued under dividend reinvestment plan			$ 860	$ 897