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Note 14 - Stock Option Plans - Fair Value of Stock Options Granted (Details) - $ / shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Volatility 35.70% 39.00% 36.50%
Risk-free interest rate 0.80% 1.80% 2.00%
Expected life (in years) (Year) 4 years 7 months 6 days 4 years 6 months 14 days 4 years 6 months
Dividend yield 0.00% 0.00% 0.00%
The weighted average grant date fair value for options issued, with the exercise price equal to market value on the date of grant (in dollars per share) $ 24.83 $ 19.98 $ 20.20