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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2020
USD ($)
customer
Dec. 31, 2019
USD ($)
customer
Dec. 31, 2018
USD ($)
Concentration Risk [Line Items]      
Term of product warranty 1 year    
Product warranty expense $ 2,915 $ 2,483 $ 3,793
Research and development costs $ 4,718 $ 3,702 $ 3,127
Accounts Receivable | Customer Concentration Risk      
Concentration Risk [Line Items]      
Number of customer | customer 0 0