Stock-based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value (Detail) |
3 Months Ended | |
|---|---|---|
Apr. 30, 2019 |
Apr. 30, 2018 |
|
| Stock options [Member] | ||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
| Volatility | 52.00% | 55.00% |
| Risk-free interest rate | 2.49% | 2.65% |
| Expected term (years) | 5 years 10 months 17 days | 5 years 3 months 29 days |
| Dividend yield | 0.00% | 0.00% |
| Employee stock purchase plan awards [Member] | ||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||
| Volatility | 48.00% | 46.00% |
| Risk-free interest rate | 2.52% | 1.95% |
| Expected term (years) | 6 months | 6 months |
| Dividend yield | 0.00% | 0.00% |