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Note 10 - Common Stock and Stock-based Compensation Plans - Valuation Assumptions (Details) - The 2002 Employee Stock Purchase Plan [Member] - Purchase Rights [Member]
3 Months Ended 9 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2022
Sep. 30, 2021
Expected dividend yield 0.00% 0.00% 0.00% 0.00%
Expected volatility, Minimum 40.00% 39.00% 38.00% 39.00%
Expected volatility, maximum 50.00% 60.00% 50.00% 60.00%
Risk-free interest rate, Minimum 0.80% 0.10% 0.50% 0.10%
Risk-free interest rate, maximum 3.00% 1.30% 3.00% 1.70%
Contractual term of up to (Month) 24 months 24 months 0 months 24 months