XML 57 R43.htm IDEA: XBRL DOCUMENT v3.20.4
Note 1 - Organization and Significant Accounting Policies - Assumptions Used to Estimate Fair Value of Employee Stock Purchase Plan (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Expected dividend yield 0.00% 0.00% 0.00%
Expected volatility, minimum 32.00% 42.00% 35.00%
Expected volatility, maximum 60.00% 43.00% 42.00%
Risk-free interest rate, minimum 0.10% 2.00% 0.70%
Risk-free interest rate, maximum 1.90% 2.50% 2.20%
Expected forfeiture 0.00% 0.00% 0.00%
Contractual term of up to (in months) (Month) 24 months 24 months 24 months