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STOCK BASED COMPENSATION - Narrative (Details) - 2013 Plan - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2021
May 21, 2021
Apr. 28, 2020
Apr. 18, 2019
Jul. 18, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of common stock shares reserved for future issuance 1,223,939 1,223,939        
Stock-based compensation expense $ 0.3 $ 0.6        
Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of common stock shares reserved for future issuance     1,500,000 350,000 66,000 20,000
Stock option vesting period   10 years