Note 6 - Equity Incentive Plan - Total Stock-based Compensation Expense (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	$ 1,311	$ 1,177	$ 4,140	$ 10,064
Cost of Sales [Member]
Stock-based compensation expense	(114)	(39)	(288)	205
Research and Development Expense [Member]
Stock-based compensation expense	50	239	318	690
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense	$ 1,147	$ 899	$ 3,534	$ 9,579

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

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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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