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Stock-Based Compensation - Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model (Details)
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Risk-free interest rate, Minimum 1.63% 0.09%
Risk-free interest rate, Maximum 2.43% 1.05%
Expected life in years 6 years 3 months  
Expected volatility, Minimum 74.49% 72.92%
Expected volatility, Maximum 76.27% 74.20%
Expected dividend yield 0.00% 0.00%
Maximum [Member]    
Expected life in years   6 years 3 months
Minimum [Member]    
Expected life in years   5 years 6 months