INCOME TAXES - Schedule of Credit Carryforwards (Details) $ in Millions	Dec. 31, 2020 USD ($)
United States | Federal
Income Taxes [Line Items]
NOL carryforwards	$ 118.9
United States | State
Income Taxes [Line Items]
NOL carryforwards	134.4
Indefinite | United States | Federal
Income Taxes [Line Items]
NOL carryforwards	75.2
R&D credit carryforwards | United States | Federal
Income Taxes [Line Items]
Tax credit carryforwards	2.3
R&D credit carryforwards | United States | State
Income Taxes [Line Items]
Tax credit carryforwards	0.9
R&D credit carryforwards | Canada
Income Taxes [Line Items]
Tax credit carryforwards	7.0
Non-capital loss carryforwards | Canada
Income Taxes [Line Items]
Tax credit carryforwards	32.2
Investment tax credit carryforwards | Canada
Income Taxes [Line Items]
Tax credit carryforwards	$ 0.8