DEBT OBLIGATIONS - Offtake Advances (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Jan. 31, 2021	Aug. 31, 2020	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Current portion of debt				$ 0	$ 2,403
Shenghe
Debt Instrument [Line Items]
Rebate income	$ 2,200	$ 9,700
Gross profit, higher than estimate					400
Long-term debt to related party
Debt Instrument [Line Items]
Debt discount				517	5,393
Current portion of debt				16,082	22,070
Offtake Advances | Long-term debt to related party
Debt Instrument [Line Items]
Required payments, percent of net profits from sales of assets			100.00%
Required payments, percent of net income			100.00%
Required payments, period from audit completion			5 days
Reduction in debt as a result of sales				52,800	12,000
Reduction due to sales to other parties				200
Outstanding balance, gross			$ 94,000	16,599	71,843
Debt discount			8,300
Current portion of debt				$ 16,600	25,700
Effective interest rate				24.75%
Reduction in debt principal due to change in price estimates				$ 2,200	10,100
Reduction in debt discount due to change in price estimates				$ 200	$ 800
Offtake Advances | Long-term debt to related party | Minimum
Debt Instrument [Line Items]
Effective interest rate				4.41%
Offtake Advances | Long-term debt to related party | Maximum
Debt Instrument [Line Items]
Effective interest rate				16.28%
Offtake Advances | Second Offtake Advance
Debt Instrument [Line Items]
Advance funded			$ 35,500