Organization and Basis of Presentation (Details)	Sep. 30, 2012 sqft property	Dec. 31, 2011 sqft property	Jan. 31, 2011 property sqft
Real Estate Properties [Line Items]
Number of properties	167		13
Square feet of gross leasable area	16,700,000	3,900,000	2,600,000
Number of shopping centers sold		36
Percentage of core portfolio	91.90%
Joint Venture [Member]
Real Estate Properties [Line Items]
Square feet of gross leasable area	2,800,000
Shopping Centers [Member]
Real Estate Properties [Line Items]
Number of properties	143
Shopping Centers [Member] | Joint Venture [Member]
Real Estate Properties [Line Items]
Number of properties	19
Development Properties [Member]
Real Estate Properties [Line Items]
Number of properties	12
Square feet of gross leasable area	2,500,000
Non-Retail Properties [Member]
Real Estate Properties [Line Items]
Number of properties	5
Land Parcels [Member]
Real Estate Properties [Line Items]
Number of properties	7
Office Buildings [Member] | Joint Venture [Member]
Real Estate Properties [Line Items]
Number of properties	2