Annual report pursuant to Section 13 and 15(d)

SHARE-BASED COMPENSATION - Assumptions Used to Calculate the Fair Value of Stock Options (Details)

v3.21.1
SHARE-BASED COMPENSATION - Assumptions Used to Calculate the Fair Value of Stock Options (Details) - 2018 Equity Incentive Plan - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 94.00% 30.00%
Risk-free interest rate 0.50% 2.40%
Expected term (years) 7 years 6 months 4 years 3 months 18 days
Dividend yield 0.00% 0.00%
Exercise price $ 2.47 $ 6.95