Impairments (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) ft²	Sep. 30, 2019 USD ($) ft²	Sep. 30, 2020 USD ($) ft²	Sep. 30, 2019 USD ($) ft²
Real Estate Properties [Line Items]
GLA | ft²	219,652	535,821	416,497	694,386
Impairment Charge | $	$ 5,746	$ 8,170	$ 16,306	$ 17,468
Northmall Centre
Real Estate Properties [Line Items]
GLA | ft²	165,350		165,350
Impairment Charge | $	$ 5,721		$ 5,721
Chamberlain Plaza
Real Estate Properties [Line Items]
GLA | ft²	54,302		54,302
Impairment Charge | $	$ 25		$ 1,538
Spring Mall
Real Estate Properties [Line Items]
GLA | ft²			45,920
Impairment Charge | $			$ 4,584
30th Street Plaza
Real Estate Properties [Line Items]
GLA | ft²			145,935
Impairment Charge | $			$ 4,449
Parcel at Lakes Crossing
Real Estate Properties [Line Items]
GLA | ft²		51,615	4,990	51,615
Impairment Charge | $		$ 5,777	$ 14	$ 5,777
Glendale Galleria
Real Estate Properties [Line Items]
GLA | ft²		119,525		119,525
Impairment Charge | $		$ 2,197		$ 2,197
Westview Center
Real Estate Properties [Line Items]
GLA | ft²		321,382		321,382
Impairment Charge | $		$ 170		$ 6,356
North Hills Village
Real Estate Properties [Line Items]
GLA | ft²		43,299		43,299
Impairment Charge | $		$ 26		$ 26
Brice Park
Real Estate Properties [Line Items]
GLA | ft²				158,565
Impairment Charge | $				$ 3,112