Commitments And Contingencies (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 09, 2011	Oct. 13, 2010
Commitments And Contingencies [Line Items]
Rent expense under operating leases	$ 1,988	$ 2,046	$ 1,934
Amount borrowed under term loan agreement	2,500
Unsecured line of credit agreement	175,000			275,000
Period for nonrecourse debt associated with contributed properties acquired	5 to 10 years
Percentage of apartment communities of owned portfolio to sell	12.00%
Restriction to sell contributed properties to limited partners	7 to 15 years
Remaining terms on sale restrictions	2 months to 5.5 years
Total guaranteed income housing tax credits to limited partners	3,000
Total secondary guaranteed income housing tax credits to limited partners					3,000
Standby Letters Of Credit [Member]
Commitments And Contingencies [Line Items]
Amount borrowed under term loan agreement	7,846
Unsecured line of credit agreement	20,000
Letter Of Credit [Member]
Commitments And Contingencies [Line Items]
Unsecured line of credit agreement	$ 275,000
Minimum [Member]
Commitments And Contingencies [Line Items]
Operating leases terms (in years)	1
Maximum [Member]
Commitments And Contingencies [Line Items]
Operating leases terms (in years)	5