Segment Reporting (Schedule Of Revenues And Net Operating Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Maximum portion of the consolidated revenue, net operating income and assets represented by each segment									10.00%
Reconciling items, Revenues									$ 154	$ 106	$ 759
Total revenues	153,267	144,621	140,687	141,398	137,139	128,627	124,946	125,867	579,973	516,579	499,176
Reconciling items, Net operating income									154	106	759
Net operating income, including reconciling items									355,436	305,541	291,883
General and administrative expenses									(29,145)	(25,138)	(24,476)
Interest expense									(130,583)	(124,126)	(121,765)
Depreciation and amortization									(144,819)	(126,668)	(118,573)
Other expenses									(3,225)	(2,871)
Income from continuing operations									47,664	26,738	27,069
Core Properties [Member]
Segment Reporting Information [Line Items]
Apartments owned, Revenues									505,966	485,422	498,417
Apartments owned, Net operating income									309,111	287,162	291,124
Non-Core Properties [Member]
Segment Reporting Information [Line Items]
Apartments owned, Revenues									73,853	31,051
Apartments owned, Net operating income									$ 46,171	$ 18,273