Summary Of Significant Accounting Policies Consolidated Statement of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounting Policies [Abstract]
Total interest costs incurred			$ 54,803	$ 57,156
Interest capitalized			(7,973)	(9,543)
Interest expense	$ 23,101	$ 23,445	46,830	47,613
Cash paid for interest, net of amounts capitalized (1)			45,577	71,832	[1]
Cash paid for income taxes			250	222
Mortgage loans assumed in acquisition			34,385	18,666
DownREIT operating partnership units redeemed for common shares			18,164	4,115
DownREIT operating partnership units issued with acquisition			0	7,742
Shares issued under dividend reinvestment plan			$ 1,047	983
Prepayment premium on senior note				$ 19,200

[1] (1) 2015 includes $19.2 million related to early extinguishment of debt.