Common Stock and Stockholders' Equity (Deficit) - Assumptions Used to Calculated Fair Value of Employee Stock Option Grants (Details) - Stock options |
3 Months Ended | |
|---|---|---|
Apr. 30, 2019 |
Apr. 30, 2018 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected dividend yield | 0.00% | 0.00% |
| Expected volatility, minimum | 42.40% | 40.90% |
| Expected volatility, maximum | 42.80% | 41.00% |
| Risk-free interest rate, minimum | 2.32% | 2.60% |
| Risk-free interest rate, maximum | 2.48% | 2.72% |
| Minimum | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected term | 5 years 6 months | 5 years 9 months 18 days |
| Maximum | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Expected term | 6 years 10 months 24 days | 6 years 1 month 6 days |