Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounting Policies [Abstract]
Total interest costs incurred			$ 64,685	$ 59,304
Interest capitalized			(10,735)	(11,639)
Interest expense	$ 27,766	$ 23,907	53,950	47,665
Cash paid for interest, net of amounts capitalized			52,997	47,995
Cash paid for income taxes			692	341
Mortgage loan refinanced			0	125,000
DownREIT operating partnership units issued with acquisition of noncontrolling interest			0	5,918
DownREIT operating partnership units redeemed for common shares			0	2,569
Shares issued under dividend reinvestment plan			$ 955	$ 1,036