Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Carrying Value of Investment (in millions)	$ 134.0	$ 126.6
Joint Venture Debt Outstanding	329.3	325.2
Partnership Interest [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value of Investment (in millions)	134.0	126.6
Deer Park [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	33.30%	33.30%
Square Feet	741,981	741,981
Carrying Value of Investment (in millions)	2.4	3.0
Joint Venture Debt Outstanding	246.9	246.9
Deer Park Warehouse [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %		33.30%
Square Feet		29,253
Carrying Value of Investment (in millions)		0
Joint Venture Debt Outstanding		1.9
Houston [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet	352,705	352,705
Carrying Value of Investment (in millions)	39.8	36.7
Joint Venture Debt Outstanding	0	0
National Harbor [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet	0	0
Carrying Value of Investment (in millions)	2.6	2.6
Joint Venture Debt Outstanding	0	0
RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet	434,562	434,562
Carrying Value of Investment (in millions)	66.8	62.2
Joint Venture Debt Outstanding	19.5	20.1
Westgate [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	58.00%	58.00%
Square Feet	332,234	332,234
Carrying Value of Investment (in millions)	19.6	19.1
Joint Venture Debt Outstanding	38.6	32.0
Wisconsin Dells [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet	265,086	265,086
Carrying Value of Investment (in millions)	2.6	2.8
Joint Venture Debt Outstanding	24.3	24.3
Other [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %
Square Feet	0	0
Carrying Value of Investment (in millions)	0.2	0.2
Joint Venture Debt Outstanding	$ 0	$ 0