Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - Employee Stock Options - $ / shares |
3 Months Ended | 9 Months Ended | ||
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Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Risk-free interest rate | 1.17% | 0.49% | 0.92% | 1.47% |
| Expected term (in years) | 6 years 29 days | 6 years 29 days | 6 years 29 days | 6 years 29 days |
| Dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
| Volatility | 114.06% | 112.02% | 113.23% | 110.81% |
| Weighted-average fair value of stock options granted | $ 5.62 | $ 9.29 | $ 11.00 | $ 11.89 |
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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 Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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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- Details
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