Note 13 - Equity-based Compensation - Summary of Stock-based Compensation Expense Included in Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock-based compensation expense	$ 106	$ 168	$ 343	$ 508
Research and Development Expense [Member]
Stock-based compensation expense	12	16	36	35
Selling and Marketing Expense [Member]
Stock-based compensation expense	18	40	64	119
General and Administrative Expense [Member]
Stock-based compensation expense	$ 76	$ 112	$ 243	$ 354

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
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