STOCK-BASED COMPENSATION - SUMMARY OF STOCK-BASED COMPENSATION EXPENSES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 1,051	$ 1,365	$ 1,582	$ 2,094
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	313	343	537	388
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	217	251	535	420
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	521	771	510	1,286
Standard and market condition-based stock options outstanding
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	179	298	194	553
RSUs, RSAs and PSUs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	852	1,056	1,349	1,518
Employee stock purchase plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 20	$ 11	$ 39	$ 23