Share-Based Compensation - Weighted-average Assumptions (Details) - Options to purchase common stock - $ / shares |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2021 |
Jun. 30, 2020 |
Jun. 30, 2021 |
Jun. 30, 2020 |
|
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||
Expected stock price volatility | 65.50% | 74.90% | 66.40% | 75.20% |
Risk free interest rate | 0.70% | 0.40% | 0.50% | 1.60% |
Expected life of options (years) | 5 years 4 months 24 days | 5 years 8 months 12 days | 5 years 4 months 24 days | 5 years 8 months 12 days |
Expected annual dividend per share (in dollars per share) | $ 0 | $ 0 | $ 0 | $ 0 |