Common Stock - Summary of Share-Based Compensation Expense (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
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Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
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| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Total stock-based compensation | $ 1,649 | $ 2,328 | $ 3,860 |
| Research and development [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Total stock-based compensation | 803 | 1,111 | 1,893 |
| General and administrative [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Total stock-based compensation | $ 846 | $ 1,217 | $ 1,967 |
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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 aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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