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Stock-Based Compensation, Employee Benefit Plans and Convertible Preferred Stock - Fair Value of Employee Stock Purchase Rights (Detail) (Employee Stock Purchase Rights [Member], 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 by Share-based Payment Award [Line Items] | |||
| Dividend yield | |||
| Expected life (years) | 6 months | 6 months | |
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Minimum [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Weighted-average grant date fair value per share | 1.28 | 1.89 | 3.18 |
| Risk-free interest rate | 0.14% | 0.05% | 0.14% |
| Expected life (years) | 6 months | ||
| Volatility | 46.60% | 45.70% | 30.43% |
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Maximum [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Weighted-average grant date fair value per share | 1.42 | 2.46 | 8.38 |
| Risk-free interest rate | 0.15% | 0.07% | 1.14% |
| Expected life (years) | 2 years 1 month 6 days | ||
| Volatility | 55.74% | 72.84% | 60.03% |
| X | ||||||||||
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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://www.xbrl.org/2003/role/presentationRef
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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://www.xbrl.org/2003/role/presentationRef
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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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- Details
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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://www.xbrl.org/2003/role/presentationRef
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