Stock-Based Compensation - Compensation expense (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
|
| Stock-based compensation expense | ||||
| Stock-based compensation expense | $ 8,189 | $ 7,985 | $ 26,428 | $ 24,725 |
| Research and development expenses | ||||
| Stock-based compensation expense | ||||
| Stock-based compensation expense | 3,408 | 1,996 | 8,995 | 6,165 |
| General and administrative expenses | ||||
| Stock-based compensation expense | ||||
| Stock-based compensation expense | 4,781 | $ 5,989 | 17,433 | $ 18,560 |
| Stock options. | ||||
| Stock-based compensation expense | ||||
| Unrecognized compensation cost | $ 67,000 | $ 67,000 | ||
| Unrecognized compensation cost expected to be recognized over a weighted average period | 2 years 7 months 6 days | |||
| Service Based Stock Options | ||||
| Stock-based compensation expense | ||||
| Purchase of an aggregate shares of common stock | 3,942,080 | |||
| Options exercise price | $ 16.01 | |||
| Weighted average grant-date fair value (per share) | $ 10.69 | |||