Note 7 - Equity Incentive Plans	3 Months Ended
Mar. 31, 2021
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	Note 7 – Equity Incentive Plans: Total compensation cost for share-based payments recognized for the three months ended March 31, 2021 and 2020 is $6,151 and $2,242, respectively. During the three months ended March 31, 2021, 34 and 37 service period stock options and performance stock options, respectively, were exercised. During the three months ended March 31, 2021, 30 service period restricted stock units were granted at a weighted average grant-date fair market value of $155.06. During the three months ended March 31, 2021, 33 service period restricted stock units vested.

Note 7 - Equity Incentive Plans

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Text Block]

Note 7 – Equity Incentive Plans:

Total compensation cost for share-based payments recognized for the three months ended March 31, 2021 and 2020 is $6,151 and $2,242, respectively. During the three months ended March 31, 2021, 34 and 37 service period stock options and performance stock options, respectively, were exercised. During the three months ended March 31, 2021, 30 service period restricted stock units were granted at a weighted average grant-date fair market value of $155.06. During the three months ended March 31, 2021, 33 service period restricted stock units vested.