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Equity Incentive Plans and Stock Based Compensation - Assumptions of Equity-Based Payments to Non-Employees (Detail) (Non-employee Stock-based Compensation Expense [Member])
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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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Non-employee Stock-based Compensation Expense [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Risk-free interest rate | 1.93% | 1.37% | 1.94% |
| Expected life (in years) | 10 years | 5 years 1 month 24 days | 5 years |
| Expected volatility | 101.00% | 92.00% | 85.00% |
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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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