Stock Plans - Summary of Fair Value Assumptions of Stock Purchase Plan (Detail) |
3 Months Ended |
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Mar. 31, 2019 | |
| Employee Stock Purchase Plan [Member] | Minimum [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Expected volatility | 51.00% |
| Risk-free interest rate | 1.30% |
| Expected term (in years) | 6 months |
| Employee Stock Purchase Plan [Member] | Maximum [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Expected volatility | 57.00% |
| Risk-free interest rate | 2.20% |
| Expected term (in years) | 2 years |
| Performance-based Stock Options [Member] | |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |
| Expected volatility | 65.00% |
| Risk-free interest rate | 2.70% |
| Cost of equity | 14.00% |
| Expected term (in years) | 6 years 4 months 24 days |
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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 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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- Definition Share based compensation arrangement by share based payment award fair value assumptions cost of equity percentage. No definition available.
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