Combined Guarantor Subsidiaries - Fair Value Measurements - Impairment of Real Estate Properties (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on Impairment	$ 135,688	$ 14,600	$ 202,121	$ 84,644
Fair Value	160,740	42,100	160,740	42,100
Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on Impairment				84,644
Fair Value		42,100		42,100
Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on Impairment			22,770
Fair Value	$ 56,300		$ 56,300
Cap Rate | Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	0.110		0.110
Discount Rate | Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	0.115		0.115
Guarantor Subsidiaries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on Impairment	$ 0	$ 0	$ 22,770	$ 0
Fair Value	56,300		56,300
Guarantor Subsidiaries | Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on Impairment			22,770
Fair Value	56,300		56,300
Equity method investments at fair value	$ 56,300		$ 56,300
Holding period			10 years
Guarantor Subsidiaries | Cap Rate | Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	0.110		0.110
Guarantor Subsidiaries | Discount Rate | Greenbrier Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value measurement input (as a percent)	0.115		0.115