Note 10 - Share-based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation	$ 797	$ 687	$ 2,593	$ 2,269
Share-based Payment Arrangement, Option [Member]
Stock-based compensation	504	455	1,660	1,450
Restricted Stock Units (RSUs) [Member]
Stock-based compensation	$ 293	$ 232	$ 933	$ 819