Stock-Based Compensation - Compensation expense (Details) - USD ($)
$ in Thousands |
1 Months Ended |
12 Months Ended |
|
Oct. 31, 2018 |
Oct. 31, 2017 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Apr. 30, 2017 |
| Stock-based compensation expense |
|
|
|
|
|
|
| Stock-based compensation expense |
|
$ 1,000
|
$ 41,271
|
$ 27,528
|
$ 17,903
|
|
| Research and development expenses |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
9,011
|
3,787
|
1,756
|
|
| General and administrative expenses |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
32,260
|
23,741
|
$ 16,147
|
|
| Employees, directors and non-employees |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Unrecognized compensation cost |
|
|
$ 70,600
|
|
|
|
| Unrecognized compensation cost expected to be recognized over a weighted average period |
|
|
2 years 2 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
|
|
|
| Purchase of an aggregate |
|
|
3,059,004
|
|
|
|
| Shares issued |
|
|
0
|
|
|
|
| Shares cancelled |
|
|
257,854
|
|
|
|
| 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 |
|
|
$ 7,600
|
$ 7,300
|
|
|
| Shares issued |
|
|
99,314
|
1,559,401
|
|
|
| Shares cancelled |
|
|
201,250
|
|
|
|
| Restricted Common Stock | Executive officer |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Shares issued |
|
|
|
|
|
460,000
|
| Market-Based Stock Options | Executive officer | Vesting based on service period |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
$ 900
|
$ 200
|
|
|
| Purchase of an aggregate |
164,400
|
|
|
|
|
|
| Market-Based Stock Options | Executive officer | Performance-based vesting |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
|
|
|
|
| Stock-based compensation expense |
|
|
$ 0
|
|
|
|
| Purchase of an aggregate |
193,400
|
|
|
|
|
|