Fair Value Measurements - Long-Lived Assets Measured at Fair Value (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment	$ 46	$ 135,688	$ 146,964	$ 202,121
Long-lived assets	166,900	160,740	166,900	160,740
Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment			146,964
Burnsville Center \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment			26,562
Long-lived assets	$ 47,300		$ 47,300
Burnsville Center \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period			10 years
Burnsville Center \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	14.5		14.5
Burnsville Center \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	15.5		15.5
Monroeville Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment			$ 107,082
Long-lived assets	$ 67,000		$ 67,000
Monroeville Mall \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period			10 years
Monroeville Mall \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	14.0		14.0
Monroeville Mall \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	14.5		14.5
Asheville Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment			$ 13,274
Long-lived assets	$ 52,600		$ 52,600
Asheville Mall \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period			10 years
Asheville Mall \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	13.25		13.25
Asheville Mall \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	14.0		14.0
Vacant Land \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment			$ 46
Greenbrier Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				22,770
Long-lived assets		56,300		56,300
Honey Creek Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				2,045
Assets book value		14,360		14,360
The Forumat Grandview \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets book value		31,559		31,559
The Forumat Grandview \| All Other
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				8,582
Eastgate Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				33,265
Long-lived assets		$ 25,100		$ 25,100
Eastgate Mall \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period				10 years
Eastgate Mall \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		14.5		14.5
Eastgate Mall \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		15.0		15.0
Mid Rivers Mall \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				$ 83,621
Long-lived assets		$ 53,340		$ 53,340
Mid Rivers Mall \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period				10 years
Mid Rivers Mall \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		12.5		12.5
Mid Rivers Mall \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		13.25		13.25
Laurel Park Place \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				$ 52,067
Long-lived assets		$ 26,000		$ 26,000
Laurel Park Place \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period				10 years
Laurel Park Place \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		13.5		13.5
Laurel Park Place \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		14.0		14.0
Prior Sales Adjustment \| Malls
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loss on impairment				$ (229)
Greenbriar Mall \| Malls \| Measurement Input, Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Holding period				10 years
Greenbriar Mall \| Malls \| Cap Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		11.5		11.5
Greenbriar Mall \| Malls \| Discount Rate (as a percent)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)		11.5		11.5