FAIR VALUE OF FINANCIAL INSTRUMENTS - Schedule of Fair Value of Financial Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	$ 9,212	$ 4,864
Fair Value Measurement on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	9,212	4,864
Fair Value Measurement on Recurring Basis | 2017 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	6,807	3,675
Fair Value Measurement on Recurring Basis | 2016 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	2,405	1,189
Fair Value Measurement on Recurring Basis | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 1 | 2017 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 1 | 2016 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 2 | 2017 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 2 | 2016 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
Fair Value Measurement on Recurring Basis | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	9,212	4,864
Fair Value Measurement on Recurring Basis | Level 3 | 2017 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	6,807	3,675
Fair Value Measurement on Recurring Basis | Level 3 | 2016 Placement Warrants
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	$ 2,405	$ 1,189