Note 7 - Stock-based Compensation - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock compensation expense	$ 1,505	$ 1,113
Research and Development Expense [Member]
Stock compensation expense	183	174
Selling and Marketing Expense [Member]
Stock compensation expense	184	229
General and Administrative Expense [Member]
Stock compensation expense	979	577
Cost of Sales [Member]
Stock compensation expense	$ 159	$ 133

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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