Note 1 - Organization and Summary of Significant Accounting Policies - Assumptions Used to Calculate Fair Value of Stock Option Awards Granted (Details) |
12 Months Ended | |
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Dec. 31, 2020 |
Dec. 31, 2019 |
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| Expected volatility, minimum | 86.00% | 76.00% |
| Expected volatility, maximum | 102.00% | 93.00% |
| Weighted-average volatility | 92.00% | 86.00% |
| Risk-free rate, minimum | 0.40% | 2.40% |
| Risk-free rate, maximum | 1.50% | 2.50% |
| Expected dividends | ||
| Minimum [Member] | ||
| Expected forfeiture rate | 7.00% | |
| Expected forfeiture rate | 15.10% | |
| Expected term (Year) | 5 years 182 days | 3 years 182 days |
| Maximum [Member] | ||
| Expected forfeiture rate | 10.50% | |
| Expected forfeiture rate | 15.50% | |
| Expected term (Year) | 6 years | 6 years |
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- Definition Represents the expected forfeiture rate, used as a valuation assumption for share-based compensation. No definition available.
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- Definition Represents the maximum expected forfeiture rate, used as a valuation assumption for share-based compensation. No definition available.
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- Definition Represents the minimum expected forfeiture rate, used as a valuation assumption for share-based compensation. No definition available.
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- Definition 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://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition 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. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition 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. No definition available.
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| X | ||||||||||
- Definition 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. No definition available.
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- Definition The maximum risk-free interest rate assumption that is used in valuing an option on its own shares. 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. No definition available.
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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. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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