FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Derivative Liabilities Reported at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	$ 23,683	$ 52,184
Private placement option derivative liability	26,339	12,094
Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	0	0
Private placement option derivative liability	0	0
Total derivative liabilities	0	0
Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	0	0
Private placement option derivative liability	0	0
Total derivative liabilities	0	0
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	23,683	52,184
Private placement option derivative liability	26,339	12,094
Total derivative liabilities	$ 50,022	$ 64,278