Note 11 - Equity Incentive Plan - Total Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stock-based compensation expense	$ 2,545	$ 2,259
Cost of Sales [Member]
Stock-based compensation expense	176	129
Research and Development Expense [Member]
Stock-based compensation expense	367	241
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	$ 2,002	$ 1,889