Stock-Based Compensation - Granted to non-employees, prior to the adoption of ASU 2018-07 (Details) - Non-employees |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Fair value of stock awards granted prior to the adoption of ASU 2018-07 | |||
| Risk-free interest rate | 0.81% | 1.10% | 2.07% |
| Expected volatility | 77.40% | 69.40% | 76.90% |
| Expected term (in years) | 6 years 29 days | 6 years 18 days | 6 years 21 days |