Note 12 - Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stock-based compensation expense	$ 605	$ 679
Cost of Sales [Member]
Stock-based compensation expense	25	31
Research and Development Expense [Member]
Stock-based compensation expense	18	42
General and Administrative Expense [Member]
Stock-based compensation expense	$ 562	$ 606