Stock-based Compensation - Restricted Stock and Restricted Stock Units Activities (Detail) - Restricted stock and restricted stock units [Member] |
3 Months Ended |
|---|---|
|
Apr. 30, 2019
$ / shares
shares
| |
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |
| Shares, Unvested, beginning balance | shares | 2,395,516 |
| Shares, Granted | shares | 407,076 |
| Shares, Vested | shares | (252,076) |
| Shares, Forfeited | shares | (17,322) |
| Shares, Unvested, ending balance | shares | 2,533,194 |
| Weighted-Average Grant-Date Fair Value, Unvested, beginning balance | $ / shares | $ 48.49 |
| Weighted-Average Grant-Date Fair Value, Granted | $ / shares | 48.11 |
| Weighted-Average Grant-Date Fair Value, Vested | $ / shares | 53.12 |
| Weighted-Average Grant-Date Fair Value, Forfeited | $ / shares | 48.20 |
| Weighted-Average Grant-Date Fair Value, Unvested, ending balance | $ / shares | $ 47.97 |