Equity Incentive Plans and Stock Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands |
12 Months Ended | |
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Dec. 31, 2017 |
Dec. 31, 2016 |
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| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | $ 1,792 | $ 109 |
| Research and Development | ||
| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | 340 | 0 |
| General and Administrative | ||
| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | $ 1,452 | $ 109 |
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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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