Stock-Based Compensation - Fair Value Monte Carlo Simulation (Details) - Restricted Stock |
3 Months Ended | |
|---|---|---|
Oct. 31, 2020 |
Oct. 31, 2019 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Volatility of common stock | 57.27% | 30.73% |
| Average volatility of peer companies | 45.37% | 36.28% |
| Average correlation coefficient of peer companies | 34.81% | 24.63% |
| Risk-free interest rate | 0.20% | 1.49% |