XML 69 R58.htm IDEA: XBRL DOCUMENT v3.21.2
Stock Based Compensation - Summary of Weighted Average Assumptions Used in Valuing Plans (Details) - $ / shares
9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Fair value at grant date $ 1.33 $ 0.98
Expected volatility 80.20% 142.10%
Risk-free interest rate 0.70% 0.70%
Expected holding period, in years 6 years 6 years 1 month 6 days
Dividend yield