Note 7 - Share-based Compensation - Nonemployee Stock Option Valuation Assumptions (Details) - Non-employee Stock Options [Member] |
9 Months Ended |
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Sep. 30, 2018 | |
Dividend yield | 0.00% |
Minimum [Member] | |
Risk-free interest rate | 2.80% |
Volatility | 78.00% |
Expected term (Year) | 7 years 328 days |
Maximum [Member] | |
Risk-free interest rate | 2.84% |
Volatility | 85.00% |
Expected term (Year) | 8 years 292 days |
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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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- 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 risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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