Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accounting Policies [Abstract]
Total interest costs incurred			$ 64,755	$ 64,685
Interest capitalized			(9,240)	(10,735)
Interest expense	$ 27,482	$ 27,766	55,515	53,950
Cash paid for interest, net of amounts capitalized			53,588	52,997
Cash paid for income taxes			419	692
DownREIT operating partnership units redeemed for common shares			11,935	0
Shares issued under dividend reinvestment plan			$ 897	$ 955