Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - $ / shares |
3 Months Ended | |
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Mar. 31, 2016 |
Mar. 31, 2015 |
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| Employee Stock Options | ||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
| Risk-free interest rate | 1.64% | 1.70% |
| Expected term (in years) | 6 years 7 days | 6 years 7 days |
| Volatility | 108.00% | 83.00% |
| Weighted-average fair value of stock options granted | $ 0.45 | $ 3.13 |
| Employee Stock Purchase Plan (ESPP) | ||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
| Risk-free interest rate | 0.56% | 0.38% |
| Expected term (in years) | 1 year 2 months 27 days | 1 year 3 months |
| Volatility | 161.00% | 51.00% |
| Weighted-average fair value of ESPP purchase rights | $ 0.22 | $ 1.59 |
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. 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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- 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.
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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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- 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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