Investments In Joint Ventures (Narrative) (Details) (USD $)	1 Months Ended		3 Months Ended			6 Months Ended	12 Months Ended			3 Months Ended							1 Months Ended	3 Months Ended
	Jan. 31, 2013	Dec. 31, 2011	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2012 acre	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 Raleigh North Carolina [Member]	Mar. 31, 2012 Orange County Florida [Member] acre	Sep. 30, 2012 Charlotte North Carolina [Member] acre	Sep. 30, 2012 Austin Texas [Member]	Dec. 31, 2012 Atlanta Georgia [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]	Oct. 31, 2012 Midwest Equity Method Investee [Member]	Dec. 31, 2012 Midwest Equity Method Investee [Member]
Number of joint ventures accounted for under equity method investments							4
Equity method investment ownership percentage		20.00%			20.00%			20.00%							15.00%	20.00%
Maximum guaranteed amount of loans utilized for construction and development activities for joint ventures			$ 0			$ 0	$ 0
Fees earned for property and asset management, construction, development, and other services to joint ventures							11,400,000	9,300,000	6,200,000
Number of units in multifamily properties acquired										0
Acres of land acquired							22.6				15.0	3.7
Number of operating properties sold		2			4	2	11						0	0			5
Number of apartment homes in operating properties sold	770	788					3,213						0	0			2,043
Sales price of property sold by unconsolidated joint venture													54,400,000	22,800,000			155,600,000
Gain on sale of property by unconsolidated joint venture			$ 14,543,000	$ 2,875,000	$ 6,394,000								$ 2,900,000	$ 1,200,000				$ 13,300,000