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Note 10 - Stock-based Compensation - Assumptions Used in the Valuation of Performance Stock (Details) - Performance Shares [Member]
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Risk-free interest rate 1.76% 0.22%
Expected life (Year) 2 years 10 months 13 days 2 years 10 months 13 days
Expected volatility 53.50% 51.40%
Expected dividend yield 0.00% 0.00%