Note 5 - Share-based Compensation - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Stock compensation expense	$ 606	$ 373
Research and Development Expense [Member]
Stock compensation expense	80	65
Selling and Marketing Expense [Member]
Stock compensation expense	166	69
General and Administrative Expense [Member]
Stock compensation expense	328	191
Cost of Sales [Member]
Stock compensation expense	$ 32	$ 48

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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