Note 11 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Outstanding, options (in shares)	5,272
Outstanding, options, weighted average exercise price (in dollars per share)	$ 0.58
Outstanding, options, contractual life (Year)	5 years	5 years 3 months 18 days
Outstanding, options, aggregate intrinsic value	$ 0
Options forfeited/expired (in shares)	(130)
Options forfeited/expired, weighted average exercise price (in dollars per share)	$ 0.44
Outstanding, options (in shares)	5,142	5,272
Outstanding, options, weighted average exercise price (in dollars per share)	$ 0.58	$ 0.58
Options vested and exercisable, options (in shares)	5,142
Options vested and exercisable, weighted average exercise price (in dollars per share)	$ 0.58
Options vested and exercisable, aggregate intrinsic 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
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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-Subparagraph (c)(1)(i)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. 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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