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STOCK-BASED COMPENSATION - Employee Stock Purchase Plan - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Jun. 25, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Proceeds from common stock issued $ 328,000 $ 277,000  
Employee Stock Purchase Plan (ESPP) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Reserved for issuance (in shares)     1,000,000
Purchase period (in months) 3 months    
Percentage of market value (in hundredths) 85.00%    
Maximum allocation of base compensation (in hundredths) 10.00%    
Maximum shares per purchase date (in shares) 12,500    
Maximum value per calendar year, per employee $ 25,000    
Common stock issued (in shares) 2,315 2,571  
Proceeds from common stock issued $ 259,000 $ 204,000  
Employee Stock Purchase Plan (ESPP) [Member] | Selling, General and Administrative Expense [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Charges to expense 22,000 22,000  
Employee Stock Purchase Plan (ESPP) [Member] | Research and Development Expense [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Charges to expense 28,000 32,000  
Employee Stock Purchase Plan (ESPP) [Member] | Cost of Sales [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Charges to expense $ 19,000 $ 19,000