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Note 13 - Stock-based Compensation - Assumptions Used in the Black-Scholes Option Pricing Model (Details) - Share-based Payment Arrangement, Option [Member] - $ / shares
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Expected life (Year) 6 years 3 months 6 years 3 months 6 years 3 months
Expected dividend yield 0.00% 0.00% 0.00%
Weighted average grant date fair value (in dollars per share) $ 128.14 $ 45.32 $ 47.84
Minimum [Member]      
Risk-free interest rate 0.80% 0.50% 2.35%
Expected volatility 45.28% 42.40% 42.52%
Maximum [Member]      
Risk-free interest rate 1.12% 1.47% 2.58%
Expected volatility 45.53% 43.83% 42.74%