Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accounting Policies [Abstract]
Total interest costs incurred			$ 116,015	$ 97,074
Interest capitalized			(17,269)	(14,507)
Interest expense	$ 36,228	$ 27,052	98,746	82,567
Cash paid for interest, net of amounts capitalized			89,447	82,118
Cash paid for income taxes			430	450
DownREIT operating partnership units issued with acquisition			18,920	0
Mortgage loans assumed with acquisition			8,903	16,951
DownREIT operating partnership units redeemed for common shares			0	11,935
Shares issued under dividend reinvestment plan			$ 1,296	$ 1,337