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Assumptions Used in Estimating Fair Value Of Stock Options Granted (Detail) (USD $)
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12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| Share based Compensation Arrangement Assumptions Used to Estimate Fair Values of Share Options Granted [Line Items] | |||
| Expected term (years) | 3 years 8 months 12 days | 4 years 1 month 24 days | 4 years 6 months 15 days |
| Volatility | 97.00% | 105.00% | 91.00% |
| Annual dividend per share | $ 0.00 | $ 0.00 | $ 0.00 |
| Risk-free interest rate | 0.77% | 1.53% | 1.94% |
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- Details
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- Definition
Share based compensation arrangement by share based payment award fair value assumptions expected dividend. No definition available.
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- Definition
Share-based compensation arrangement by share-based payment award fair value assumptions expected term one. No definition available.
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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://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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