Note 11 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Outstanding, stock options (in shares)	7,123
Outstanding, weighted average exercise price (in dollars per share)	$ 0.54
Outstanding, weighted average remaining contractual life (Year)	6 years 10 months 24 days	7 years 6 months
Outstanding, aggregate intrinsic value	$ 0	$ 0
Options forfeited/expired, stock options (in shares)	(913)
Options forfeited/expired, weighted average exercise price (in dollars per share)	$ 0.44
Outstanding, stock options (in shares)	6,210	7,123
Outstanding, weighted average exercise price (in dollars per share)	$ 0.56	$ 0.54
Options vested and exercisable, stock options (in shares)	6,353
Options vested and exercisable, weighted average exercise price (in dollars per share)	$ 0.55
Options vested and exercisable, weighted average remaining contractual life (Year)	6 years 8 months 12 days
Options vested and exercisable, aggregate instrinsic value	$ 0

For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-Subparagraph (c)(1)(iv)
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Weighted average price of options that were either forfeited or expired.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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