Note 10 - Share-based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock-based compensation	$ 803	$ 694	$ 1,582	$ 1,440
Share-based Payment Arrangement, Option [Member]
Stock-based compensation	495	432	995	879
Restricted Stock Units (RSUs) [Member]
Stock-based compensation	$ 308	$ 262	$ 587	$ 561