Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 jvs partnerships	Jun. 30, 2011	Dec. 31, 2011
Commitments And Contingencies [Line Items]
Number of downREIT real estate ventures	4
Shares issued in exchange for noncontrolling interests	$ 0	$ 0
Aggregate redemption value of interests	42		35
Number of unconsolidated joint ventures with partner	2
Capital Additions [Member]
Commitments And Contingencies [Line Items]
Construction contract commitment	$ 67.3
Capital Additions [Member] | Minimum [Member]
Commitments And Contingencies [Line Items]
Construction contract period, months	12
Capital Additions [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Construction contract period, months	36