STOCK-BASED COMPENSATION - SUMMARY OF STOCK-BASED COMPENSATION EXPENSES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 531	$ 729
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	224	45
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	318	168
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	(11)	516
Standard and market condition-based stock options outstanding
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	15	255
RSUs and RSAs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	497	462
Employee stock purchase plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 19	$ 12