Stock-Based Payments - Weighted-Average Assumptions to Estimate Fair Value of Stock Options (Details) - $ / shares |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Weighted-average risk-free interest rate | 2.46% | 2.49% | ||
| Expected option term (in years) | 6 years 7 days | 6 years 10 days | ||
| Volatility | 91.49% | 90.34% | ||
| Stock Option | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Weighted-average risk-free interest rate | 1.88% | 2.87% | ||
| Expected option term (in years) | 6 years 29 days | 6 years 29 days | ||
| Volatility | 89.91% | 89.71% | ||
| Weighted-average grant date fair value of options granted (in dollars per share) | $ 5.10 | $ 8.15 | ||
| 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
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- 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.
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Details
|