Annual report pursuant to Section 13 and 15(d)

STOCK BASED COMPENSATION - Common Stock to Employees (Details)

v3.20.4
STOCK BASED COMPENSATION - Common Stock to Employees (Details) - Employee - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Risk-free interest rate, Minimum 0.30% 1.70%
Risk-free interest rate, Maximum 1.70% 2.60%
Expected volatility, Minimum 52.70% 52.70%
Expected volatility, Maximum 54.20% 53.60%
Expected life, Minimum (in years) 5 years 10 months 24 days 5 years 7 months 6 days
Expected life, Maximum (in years) 6 years 3 months 18 days 6 years 1 month 6 days
Fair value of Common Stock, Minimum $ 1.40  
Fair value of Common Stock, Maximum $ 7.98  
Fair value of Common Stock   $ 3.34