RELATIONSHIP AND AGREEMENTS WITH SHENGHE - Activity Related to Modifications (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended			9 Months Ended
	Jun. 05, 2020	Jun. 20, 2017	May 31, 2017	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Related Party Transaction [Line Items]
Settlement charge				$ 0	$ 0	$ 66,600	$ 0	$ 66,615
Affiliated Entity | First Additional Advance
Related Party Transaction [Line Items]
Advances		$ 30,000
Affiliated Entity | Initial Prepayment Amount
Related Party Transaction [Line Items]
Advances			$ 50,000
Increase in advances		30,000
Shenghe | Affiliated Entity
Related Party Transaction [Line Items]
Settlement charge	$ (66,615)
Shenghe | Affiliated Entity | First Additional Advance
Related Party Transaction [Line Items]
Advances		30,000
Debt fair value		26,500
Deferred revenue arrangement modification fair value		3,500
Preferred interest, fair value		2,300
Shenghe | Affiliated Entity | Initial Prepayment Amount
Related Party Transaction [Line Items]
Increase in advances	30,000	$ 30,000
Shenghe | Affiliated Entity | Shenghe Implied Discount
Related Party Transaction [Line Items]
Shenghe Implied Discount, percentage of contractual gross profit		36.00%
Shenghe | Affiliated Entity | Stage II optimization project
Related Party Transaction [Line Items]
Expected advances	$ 200,000