Quarterly report pursuant to Section 13 or 15(d)

Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details)

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Investments in Unconsolidated Real Estate Joint Ventures (Unconsolidated Real Estate Joint Ventures) (Details)
ft² in Thousands, $ in Thousands
Sep. 30, 2018
USD ($)
ft²
Dec. 31, 2017
USD ($)
ft²
National Harbor and RioCan Canada [Member]    
Schedule of Equity Method Investments [Line Items]    
Carrying Value of Investment $ 111,300  
National Harbor [Member]    
Schedule of Equity Method Investments [Line Items]    
Ownership % 50.00% 50.00%
Square Feet | ft² 341 341
Carrying Value of Investment $ 600 $ 2,500
RioCan Canda [Member]    
Schedule of Equity Method Investments [Line Items]    
Ownership % 50.00% 50.00%
Square Feet | ft² 923 923
Carrying Value of Investment $ 110,700 $ 115,800
Columbus National Harbor RioCan Canada [Member]    
Schedule of Equity Method Investments [Line Items]    
Carrying Value of Investment   $ 119,400
Columbus, Charlotte and Galveston/Houston [Member]    
Schedule of Equity Method Investments [Line Items]    
Equity Method Investment Reported In Liabilities $ (26,700)  
Columbus [Member]    
Schedule of Equity Method Investments [Line Items]    
Ownership % 50.00% 50.00%
Square Feet | ft² 355 355
Carrying Value of Investment   $ 1,100
Equity Method Investment Reported In Liabilities $ (1,100)  
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 $ (10,300) $ (4,100)
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 $ (15,300) $ (13,000)
Charlotte and Galveston/Houston [Member]    
Schedule of Equity Method Investments [Line Items]    
Equity Method Investment Reported In Liabilities   (17,100)
Unconsolidated Properties [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 360,600 351,259
Unconsolidated Properties [Member] | National Harbor [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 86,700 86,400
Unconsolidated Properties [Member] | RioCan Canda [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 10,200 11,100
Unconsolidated Properties [Member] | Columbus [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 84,700 84,400
Unconsolidated Properties [Member] | Charlotte [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 99,500 89,800
Unconsolidated Properties [Member] | Galveston/Houston [Member]    
Schedule of Equity Method Investments [Line Items]    
Total joint venture debt, net 79,500 79,400
Mortgages [Member] | Unconsolidated Properties [Member]    
Schedule of Equity Method Investments [Line Items]    
Net discount and debt origination costs $ 1,400 $ 1,400