Note 9 - Equity Plans and Related Equity Activities - Schedule of Valuation Assumptions of Stock Options (Details)	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Equity Stock Purchase Plan [Member]
Expected volatility, minimum	83.00%
Expected volatility, maximum	93.00%
Risk-free interest rate, minimum	4.37%
Risk-free interest rate, maximum	4.60%
Expected dividend	0.00%
Minimum [Member] \| Equity Stock Purchase Plan [Member]
Expected term (years) (Year)	6 months
Maximum [Member] \| Equity Stock Purchase Plan [Member]
Expected term (years) (Year)	2 years
Share-Based Payment Arrangement, Option [Member]
Expected volatility, minimum	71.00%
Expected volatility, maximum	86.00%
Expected volatility		88.00%
Risk-free interest rate, minimum	0.53%	0.60%
Risk-free interest rate, maximum	4.07%	1.20%
Expected dividend	0.00%	0.00%
Share-Based Payment Arrangement, Option [Member] \| Minimum [Member]
Expected term (years) (Year)	5 years	5 years 7 months 13 days
Share-Based Payment Arrangement, Option [Member] \| Maximum [Member]
Expected term (years) (Year)	6 years 21 days	10 years

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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