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Note 5 - Share-based Compensation - Black-Scholes Options Pricing Model (Details)
6 Months Ended
Jun. 30, 2021
Risk-Free interest rate, minimum 0.13%
Risk-Free interest rate, maximum 0.55%
Expected stock price volatility, minimum 54.52%
Expected stock price volatility, maximum 56.07%
Minimum [Member]  
Expected life of options (Year) 2 years
Maximum [Member]  
Expected life of options (Year) 6 years 3 months