Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details) ft² in Thousands, $ in Thousands	Mar. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($) ft²
Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 336,066	$ 335,971
Columbus National Harbor RioCan Canada [Member]
Schedule of Equity Method Investments [Line Items]
Carrying Value of Investment	127,900	128,100
Columbus National Harbor RioCan Canada [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 181,400	$ 181,400
Columbus [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	355	355
Carrying Value of Investment	$ 6,600	$ 6,700
Columbus [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 84,200	$ 84,200
National Harbor [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	341	341
Carrying Value of Investment	$ 3,200	$ 4,100
National Harbor [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 86,200	$ 86,100
RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	926	901
Carrying Value of Investment	$ 118,100	$ 117,300
RioCan Canda [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	11,000	11,100
Charlotte and Galveston/Houston [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Reported In Liabilities	(7,100)	(6,300)
Charlotte and Galveston/Houston [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 154,700	$ 154,600
Charlotte [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	398	398
Equity Method Investment Reported In Liabilities	$ (2,600)	$ (2,500)
Charlotte [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 89,800	$ 89,700
Galveston/Houston [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	353	353
Equity Method Investment Reported In Liabilities	$ (4,500)	$ (3,800)
Galveston/Houston [Member] | Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	$ 64,900	$ 64,900