Common Stock - Summary of Fair Value of Each Stock Award for Employees and Directors (Detail) |
9 Months Ended | |
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Sep. 30, 2018 |
Sep. 30, 2017 |
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| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] | ||
| Risk-free interest rates | 2.93% | 1.95% |
| Expected dividend yield | 0.00% | 0.00% |
| Expected life | 5 years 8 months 4 days | 6 years |
| Expected volatility | 88.23% | 86.06% |
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- References 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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- 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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