Commitments and Contingencies (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
300 properties designed and built in violation of accessibility requirements	300
Projects in various stages of development	5
Units in various stages of development	1,267
Consolidated Project Under Development Commitment Fund	$ 283,100,000
Various stages of development with estimated completion dates ranging through June 30, 2011	Jun. 30, 2014
Number Of Unconsolidated Projects	2
Number Of Apartments Units Under Development Unconsolidated Projects	945
Estimated completion period of project	Dec. 31, 2013
Land purchase price	76,100,000
Business Acquisition, Cost of Acquired Entity, Purchase Price	968,545,000
Investment in Joint Venture	194,700,000
Noncontrolling Interests - Partially Owned Properties	75,428,000	74,306,000
Joint Venture Partner [Member]
Land purchase price	57,900,000
Business Acquisition, Cost of Acquired Entity, Purchase Price	75,700,000
Noncontrolling Interests - Partially Owned Properties	81,800,000
Company's Portion [Member]
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 102,500,000