Stock Plans (Details) - USD ($) $ in Thousands |
3 Months Ended | |
---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
|
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
Total stock-based compensation expense | $ 136 | $ 432 |
Research and development [Member] | ||
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
Total stock-based compensation expense | 77 | 163 |
General and administrative [Member] | ||
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
Total stock-based compensation expense | $ 59 | $ 269 |