Stockholders' Equity - Summary of Restricted Stock Unit (RSU) Activity (Detail) - Restricted Stock Units (RSUs) [Member] |
3 Months Ended |
|---|---|
|
Apr. 30, 2018
$ / shares
shares
| |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
| Unreleased restricted stock units, Beginning Balance | shares | 2,901,736 |
| Unreleased restricted stock units, RSUs granted | shares | 637,710 |
| Unreleased restricted stock units, RSUs vested | shares | (319,124) |
| Unreleased restricted stock units, RSUs forfeited/cancelled | shares | (62,247) |
| Unreleased restricted stock units, Ending Balance | shares | 3,158,075 |
| Weighted average grant date fair value, Beginning Balance | $ / shares | $ 38.14 |
| Weighted average grant date fair value, RSUs granted | $ / shares | 69.94 |
| Weighted average grant date fair value, RSUs vested | $ / shares | 34.58 |
| Weighted average grant date fair value, RSUs forfeited/cancelled | $ / shares | 39.70 |
| Weighted average grant date fair value, Ending Balance | $ / shares | $ 44.89 |