Variable Interest Entities (Details 1) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Basis Of Presentation [Line Items]
Net real estate related to Variable Interest Entities	$ 427,043,000	$ 599,302,000
Non-recourse property debt related to Variable Interest Entities	372,489,000	495,012,000
Variable Interest Entity, Not Primarily Beneficiary Held Through Consolidated Tax Credit Funds in Which Company Holds Substantially All Economic Interests [Member]
Basis Of Presentation [Line Items]
Maximum risk or loss related to investment in, receivable from, or contractual obligation to advance funds to unconsolidated VIEs	4,000,000
Receivables From Unconsolidated Variable Interest Entities [Member]
Basis Of Presentation [Line Items]
Maximum risk or loss related to investment in, receivable from, or contractual obligation to advance funds to unconsolidated VIEs	215,800,000
Variable Interest Entity, Primary Beneficiary [Member]
Basis Of Presentation [Line Items]
Net real estate related to Variable Interest Entities	427,000,000
Non-recourse property debt related to Variable Interest Entities	$ 372,500,000
Number of apartment properties owned by consolidated variable interest entities	52
Number Of Units In Apartment Properties Owned By Variable Interest Entities	8,100
Number of consolidated properties in portfolio	66
Variable Interest Entity, Not Primary Beneficiary [Member]
Basis Of Presentation [Line Items]
Number of apartment properties owned by consolidated variable interest entities	92
Number Of Units In Apartment Properties Owned By Variable Interest Entities	2,360
Number of consolidated properties in portfolio	39