Note 9 - Share-based compensation - Stock Option Activity (Details) - Common Stock [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Weighted average grant date fair value of stock options granted (in dollars per share)	$ 9.43	$ 12.55	$ 18.67
Intrinsic value of stock options exercised (in thousands)	$ 648	$ 3,535	$ 25,912
Intrinsic value of stock options vested (in thousands)	$ 4,369	$ 4,805	$ 1,965