Combined Guarantor Subsidiaries - Dispositions - Summary (Details) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($) outparcel	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($) outparcel	Sep. 30, 2019 USD ($) outparcel	Sep. 30, 2018 USD ($) outparcel	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on Extinguishment of Debt	$ 0		$ 0		$ 71,722	$ 0
Loss on impairment	$ 135,688		14,600		202,121	84,644
Gain (loss) on sales of real estate assets					$ 13,811	15,998
Number of outparcels sold | outparcel	2				3
Acadania Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment							$ 1,593	$ 43,007
Non-cash default interest expense		$ 305
Malls
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment						84,644
Non-recourse loans on operating properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Balance of Non-recourse Debt	$ 163,476				$ 163,476
Gain on Extinguishment of Debt					71,722
Non-recourse loans on operating properties | Malls | Acadania Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Balance of Non-recourse Debt	119,760				119,760
Gain on Extinguishment of Debt					61,796
Guarantor Subsidiaries
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on Extinguishment of Debt	0		0		61,796	0
Loss on impairment	0		$ 0		22,770	0
Gain (loss) on sales of real estate assets				$ 698	20	$ 2,406
Number of outparcels sold | outparcel				1		5
Guarantor Subsidiaries | Restatement Adjustment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sales of real estate assets				$ 0
Guarantor Subsidiaries | Acadania Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment								$ 43,007
Non-cash default interest expense		$ 305
Guarantor Subsidiaries | Non-recourse loans on operating properties | Malls | Acadania Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Balance of Non-recourse Debt	$ 119,760				119,760
Gain on Extinguishment of Debt					$ 61,796