Stock-Based Compensation - Compensation expense (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2021 |
Mar. 31, 2020 |
|
| Stock-based compensation expense | ||
| Stock-based compensation expense | $ 8,642 | $ 8,488 |
| Research and development expenses | ||
| Stock-based compensation expense | ||
| Stock-based compensation expense | 2,531 | 2,111 |
| General and administrative expenses | ||
| Stock-based compensation expense | ||
| Stock-based compensation expense | 6,111 | $ 6,377 |
| Stock options. | ||
| Stock-based compensation expense | ||
| Unrecognized compensation cost | $ 60,400 | |
| Unrecognized compensation cost expected to be recognized over a weighted average period | 2 years 4 months 24 days | |
| Service Based Stock Options | ||
| Stock-based compensation expense | ||
| Purchase of an aggregate shares of common stock | 2,459,661 | |
| Options exercise price | $ 12.53 | |
| Weighted average grant-date fair value (per share) | $ 8.37 | |