Financing Arrangement - Narrative (Details) ft² in Thousands, $ in Thousands	Sep. 30, 2009 ft²	Sep. 30, 2018 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Schedule of Joint Ventures [Line Items]
Distributions in excess of co-venture obligation		$ 0		$ 31,150
Financing arrangement obligation		384,431		0
Accumulated deficit		$ (1,520,209)		$ (830,279)
Discount rate		5.80%
Joint Venture | Chandler Freehold
Schedule of Joint Ventures [Line Items]
Distributions in excess of co-venture obligation			$ 31,150
Financing Arrangement
Schedule of Joint Ventures [Line Items]
Operating income multiple		20.8333333333
Financing Arrangement | Minimum
Schedule of Joint Ventures [Line Items]
Market rents per square foot		20
Financing Arrangement | Maximum
Schedule of Joint Ventures [Line Items]
Market rents per square foot		225
Financing Arrangement | Joint Venture | Chandler Freehold | ASU 2014-09 | Difference between revenue guidance in effect before and after topic 606
Schedule of Joint Ventures [Line Items]
Financing arrangement obligation			393,709
Accumulated deficit			$ 424,859
Financing Arrangement | Chandler Freehold
Schedule of Joint Ventures [Line Items]
Percentage of loan assumed by third party	49.90%
Financing Arrangement | Chandler Fashion Center
Schedule of Joint Ventures [Line Items]
Property area (in square feet) | ft²	1,316
Financing Arrangement | Freehold Raceway Mall
Schedule of Joint Ventures [Line Items]
Property area (in square feet) | ft²	1,672