Stockholders' Equity - Stock Option Plan Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
Total stock based compensation expense | $ 3,146 | $ 2,755 | $ 9,820 | $ 8,984 |
Research and Development | ||||
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
Total stock based compensation expense | 1,534 | 1,124 | 4,341 | 4,325 |
General and Administrative | ||||
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||||
Total stock based compensation expense | $ 1,612 | $ 1,631 | $ 5,479 | $ 4,659 |