Stock-Based Compensation - Compensation expense (Details) - USD ($)
$ in Thousands |
1 Months Ended |
12 Months Ended |
|
Oct. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2018 |
| Stock-based compensation expense |
|
|
|
|
|
| Stock-based compensation expense |
$ 1,000
|
$ 27,528
|
$ 17,903
|
$ 147
|
|
| Research and development expenses |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Stock-based compensation expense |
|
3,787
|
1,756
|
107
|
|
| General and administrative expenses |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Stock-based compensation expense |
|
$ 23,741
|
$ 16,147
|
$ 40
|
|
| Employees, directors and non-employees |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Unrecognized compensation cost |
|
|
|
|
$ 89,600
|
| Unrecognized compensation cost expected to be recognized over a weighted average period |
|
2 years 8 months 12 days
|
|
|
|
| Chairman |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Issuance of common stock for one‑time bonus payment (in shares) |
213,439
|
|
|
|
|
| Stock options. |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Stock-based compensation expense |
|
$ 2,200
|
|
|
|
| Shares issued |
|
|
|
|
232,500
|
| Purchase of an aggregate |
|
10,405,323
|
|
|
|
| Stock options. | Performance-based vesting |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Purchase of an aggregate |
|
447,000
|
|
|
|
| Restricted Common Stock |
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
| Stock-based compensation expense |
|
$ 7,300
|
|
|
|
| Shares issued |
|
5,227,014
|
5,227,014
|
|
1,559,401
|
| Unvested restricted common stock beginning of period |
|
5,227,014
|
|
|
|