Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounting Policies [Abstract]
Total interest costs incurred	$ 32,580	$ 32,276
Interest capitalized	(4,547)	(6,092)
Interest expense	28,033	26,184
Cash paid for interest, net of amounts capitalized	32,485	31,832
Cash paid for income taxes	7	57
DownREIT operating partnership units redeemed for common shares	7,551	0
Shares issued under dividend reinvestment plan	$ 455	$ 477