Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details) ft² in Thousands, $ in Thousands	Jun. 30, 2019 USD ($) ft²	Dec. 31, 2018 USD ($) ft²
RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	762	924
Carrying Value of Investment	$ 96,300	$ 96,000
Columbus, Charlotte, National Harbor and Galveston/Houston [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Reported In Liabilities	$ (39,500)	$ (32,500)
Columbus [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	355	355
Equity Method Investment Reported In Liabilities	$ (2,300)	$ (1,600)
Charlotte [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	399	398
Equity Method Investment Reported In Liabilities	$ (11,500)	$ (10,800)
National Harbor [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	341	341
Equity Method Investment Reported In Liabilities	$ (5,200)	$ (5,100)
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	$ (20,500)	$ (15,000)
Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	368,072	367,865
Unconsolidated Properties [Member] | RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	9,500	9,300
Unconsolidated Properties [Member] | Columbus [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	84,900	84,700
Unconsolidated Properties [Member] | Charlotte [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	99,500	99,500
Unconsolidated Properties [Member] | National Harbor [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	94,400	94,500
Unconsolidated Properties [Member] | Galveston/Houston [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	79,700	79,600
Mortgages [Member] | Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Net discount and debt origination costs	$ 1,300	$ 1,400