Note 11 - Summary of Stock Options - Stock-based Compensation Expense Included in the Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation expense	$ 710	$ 496
Cost of Sales [Member]
Stock-based compensation expense	60	32
Research and Development Expense [Member]
Stock-based compensation expense	87	40
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	$ 564	$ 424

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

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