Employee Stock Purchase Plan and Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Recognized (Details) - USD ($) |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||||
| Total stock-based compensation expense | $ 321 | $ 593 | $ 802 | $ 1,126 |
| Research and Development | ||||
| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||||
| Total stock-based compensation expense | 65 | 19 | 160 | 91 |
| General and Administrative | ||||
| Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] | ||||
| Total stock-based compensation expense | $ 256 | $ 574 | $ 642 | $ 1,035 |