Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details) ft² in Thousands, $ in Thousands	Mar. 31, 2021 USD ($) ft²	Dec. 31, 2020 USD ($) ft²
Columbus and RioCan Canada
Schedule of Equity Method Investments [Line Items]
Carrying Value of Investment	$ 89,500	$ 94,600
Columbus [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	355	355
Carrying Value of Investment	$ 1,600	$ 2,000
RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	665	765
Carrying Value of Investment	$ 87,900	$ 92,600
Charlotte, National Harbor and Galveston/Houston
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Reported In Liabilities	$ (34,400)	$ (40,700)
Charlotte [Member]
Schedule of Equity Method Investments [Line Items]
Ownership %	50.00%	50.00%
Square Feet | ft²	399	399
Equity Method Investment Reported In Liabilities	$ (12,400)	$ (12,800)
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	$ (9,800)	$ (8,400)
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	$ (12,200)	$ (19,500)
Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	329,249	344,856
Unconsolidated Properties [Member] | Columbus [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	70,800	70,800
Unconsolidated Properties [Member] | RioCan Canda [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	0	0
Unconsolidated Properties [Member] | Charlotte [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	99,600	99,600
Unconsolidated Properties [Member] | National Harbor [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	94,500	94,500
Unconsolidated Properties [Member] | Galveston/Houston [Member]
Schedule of Equity Method Investments [Line Items]
Total joint venture debt, net	64,300	80,000
Mortgages [Member] | Unconsolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Net debt origination costs	$ 1,300	$ 1,100