Note 14 - Stock Based Compensation - Assumptions to Calculate Fair Value of Each Employee Stock Option (Details) - Time-based Stock Option [Member] |
12 Months Ended | |
|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Expected term (Year) | 6 years 2 months 12 days | 6 years 2 months 12 days |
| Risk-free interest rate, minimum | 0.90% | |
| Risk-free interest rate, maximum | 1.30% | |
| Expected volatility | 90.00% | 83.00% |
| Expected dividend rate | 0.00% | 0.00% |
| Minimum [Member] | ||
| Expected term (Year) | 6 years | |
| Risk-free interest rate, minimum | 0.40% | |
| Maximum [Member] | ||
| Risk-free interest rate, maximum | 1.50% | |