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Note 10 - Stock-based Compensation - Assumptions Used in the Black-Scholes Option Pricing Model (Details) - Share-Based Payment Arrangement, Option [Member]
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Risk-free interest rate 1.94%  
Expected life (Year) 6 years 3 months 6 years 3 months
Expected volatility 45.95%  
Expected dividend yield 0.00% 0.00%
Minimum [Member]    
Risk-free interest rate   0.80%
Expected volatility   45.28%
Maximum [Member]    
Risk-free interest rate   0.96%
Expected volatility   45.35%