Stock and Employee Benefit Plans - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands |
12 Months Ended | |
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Dec. 31, 2017 |
Dec. 31, 2016 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Stock-based compensation | $ 3,046 | $ 1,905 |
| Research and development | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Stock-based compensation | 844 | 599 |
| General and administrative | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Stock-based compensation | $ 2,202 | $ 1,306 |
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. 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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