Note 7 - Share-based Compensation - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock compensation expense	$ 1,145	$ 818	$ 2,258	$ 1,349
Research and Development Expense [Member]
Stock compensation expense	222	168	397	235
Selling and Marketing Expense [Member]
Stock compensation expense	96	171	325	326
General and Administrative Expense [Member]
Stock compensation expense	699	439	1,275	716
Cost of Sales [Member]
Stock compensation expense	$ 128	$ 40	$ 261	$ 72

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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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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