Assumptions Used in Estimating Fair Value of Stock Options Granted (Detail) - 2002 Stock Incentive Plan |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected term (years) | 5 years 11 months 16 days | 5 years 9 months 18 days | 3 years 9 months 29 days |
| Volatility | 86.00% | 90.00% | 94.00% |
| Risk-free interest rate | 1.39% | 1.64% | 1.66% |
| 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://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| 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 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://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Details
|