Stock-based Compensation - Classification of Stock-based Compensation (Detail) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Apr. 30, 2019 |
Apr. 30, 2018 |
|
| Stock-based compensation: | ||
| Total stock-based compensation | $ 16,460 | $ 14,195 |
| Cost of revenue [Member] | ||
| Stock-based compensation: | ||
| Total stock-based compensation | 267 | 315 |
| Research and development [Member] | ||
| Stock-based compensation: | ||
| Total stock-based compensation | 10,204 | 8,760 |
| Selling, general and administrative [Member] | ||
| Stock-based compensation: | ||
| Total stock-based compensation | $ 5,989 | $ 5,120 |