Investments in Unconsolidated Real Estate Joint Ventures Unconsolidated Real Estate Joint Ventures (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Houston [Member] sqft	Nov. 02, 2012 Houston [Member] sqft	Dec. 31, 2011 Houston [Member] sqft	Dec. 31, 2012 Deer Park Warehouse [Member] sqft	Dec. 31, 2011 Deer Park Warehouse [Member] sqft	Dec. 31, 2012 Deer Park [Member] sqft	Dec. 31, 2011 Deer Park [Member] sqft	Oct. 31, 2003 Deer Park [Member]	Dec. 31, 2012 Wisconsin Dells [Member] sqft	Dec. 31, 2011 Wisconsin Dells [Member] sqft	Dec. 31, 2012 National Harbor [Member] sqft	Dec. 31, 2011 National Harbor [Member] sqft	Dec. 31, 2012 RioCan Canda [Member] sqft	Dec. 31, 2011 RioCan Canda [Member] sqft	Dec. 31, 2012 Westgate [Member] sqft	Nov. 02, 2012 Westgate [Member] sqft	Dec. 31, 2012 Other [Member] sqft	Dec. 31, 2011 Other [Member] sqft
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			50.00%		50.00%	33.30%	33.30%	33.30%	33.30%	33.30%	50.00%	50.00%	50.00%	50.00%	50.00%	50.00%	58.00%
Area of Real Estate Property			352,705	353,000	0	29,253	29,253	741,981	656,788		265,086	265,086	0	0	434,562	159,391	332,234	332,000	0	0
Equity Method Investments	$ 126.6	$ 28.5	$ 36.7		$ 7.9	$ 0	$ 0	$ 3.0	$ 5.4		$ 2.8	$ 4.0	$ 2.6	$ 0.9	$ 62.2	$ 10.0	$ 19.1		$ 0.2	$ 0.3
Joint Venture Debt	$ 325.2	$ 303.2	$ 0		$ 0	$ 1.9	$ 2.3	$ 246.9	$ 246.9		$ 24.3	$ 24.3	$ 0	$ 0	$ 20.1	$ 29.7	$ 32.0		$ 0	$ 0