Investment in Unconsolidated Real Estate Joint Ventures (Narrative) (Details) (USD $)				12 Months Ended			3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Deer Park [Member] sqft	Dec. 31, 2008 Deer Park Warehouse [Member]	Sep. 30, 2012 Deer Park Warehouse [Member] sqft	Jun. 30, 2008 Deer Park Warehouse [Member]	Sep. 30, 2012 Deer Park Warehouse [Member] Warehouse Mortgage [Member]	Sep. 30, 2012 Deer Park Warehouse [Member] Warehouse Mortgage [Member]	Jun. 30, 2008 Deer Park Warehouse [Member] Warehouse Mortgage [Member]	Sep. 30, 2011 Houston [Member]	Sep. 30, 2012 Houston [Member] sqft	Jun. 30, 2011 National Harbor [Member]	Sep. 30, 2012 National Harbor [Member] sqft	Dec. 31, 2011 National Harbor [Member]	Sep. 30, 2012 RioCan Canda [Member] sqft	Sep. 30, 2012 Westgate [Member] sqft	Jun. 30, 2012 Westgate [Member]	Sep. 30, 2012 Westgate [Member] sqft	Sep. 30, 2011 Cookstown Property [Member] RioCan Canda [Member]	Dec. 31, 2011 Cookstown Property [Member] RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Joint Venture Formation Date				6/1/2008						6/1/2011		5/1/2011					5/4/2012
Business Acquisition, Cost of Acquired Entity, Purchase Price						$ 3,300,000														$ 61,200,000
Equity Method Investment, Ownership Percentage			33.30%		33.30%						50.00%		50.00%		50.00%	58.00%		58.00%
Debt Instrument, Maturity Date								May 17, 2011
Repayments of Long-term Debt							500,000
Debt Instrument, Deferred Interest Rate							Prime + 5.5%
Debt Instrument, Interest Rate Terms							LIBOR + 1.85%									LIBOR + 1.75%
Number of Outlet Stores											85		80			80		80
Phase One Square Footage											353,000
Estimated Square Footage of Real Estate Property When Completed											470,000		350,000					330,000,000
Purchase Price of Land Acquired										5,600,000
Company Portion of Contributed Capital to the Joint Venture											27,800,000			1,200,000	15,100,000			19,400,000
Remaining Construction Commitments											17,000,000							17,600,000
Business Acquisition, Effective Date of Acquisition																			Dec. 09, 2011
Square Footage of Real Estate Property			741,981		29,253						352,705		0		155,522	0		0
Abandoned development costs															1,300,000
Secured Debt							1,800,000	1,800,000	2,300,000
Business Acquisition, Amount of Cash Paid and Debt Assumed																				47,400,000
Business Acquisition, Contingent Consideration, Potential Cash Payment																				13,800,000
Business Acquisition, Purchase Price Allocation, Liabilities Assumed																				29,600,000
Business Acquisition, Debt Assumed, Stated Interest Rate																				5.10%
Joint Venture Debt																43,800,000		43,800,000
Equity Method Investments	82,700,000	28,500,000	3,500,000		0						28,500,000		1,200,000		25,900,000	19,500,000		19,500,000
Joint Venture Debt	$ 288,900,000		$ 246,900,000		$ 1,800,000						$ 0		$ 0		$ 0	$ 15,900,000		$ 15,900,000