Note 11 - Equity Incentive Plan - Total Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Stock-based compensation expense	$ 2,797	$ 2,240	$ 5,056	$ 2,033
Cost of Sales [Member]
Stock-based compensation expense	214	216	343	362
Research and Development Expense [Member]
Stock-based compensation expense	402	156	643	352
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	$ 2,181	$ 1,868	$ 4,070	$ 1,319

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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