Note 9 - Share-based compensation - Stock Option Activity (Details) - Common Stock [Member] - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
Weighted average grant date fair value of stock options granted (in dollars per share) | $ 18.67 | $ 11.99 | $ 10.02 |
Exercised, aggregate intrinsic value | $ 25,912 | $ 8,280 | $ 10,621 |
Intrinsic value of stock options vested (in thousands) | $ 1,965 | $ 1,891 | $ 2,719 |