Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Apr. 30, 2018 |
Apr. 30, 2017 |
|
| Foreign currency forward contracts [Member] | ||
| Foreign Currency Fair Value Hedge Derivative [Line Items] | ||
| Foreign currency gains (losses) recognized | $ 0.5 | $ (0.6) |