Derivative Instruments (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Apr. 30, 2018 |
Apr. 30, 2017 |
|
| Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||
| Net foreign currency exchange gain (loss) | $ (0.7) | $ 0.9 |
| Notional amount of derivative financial instruments outstanding | $ 1,400.0 | $ 800.0 |
| Average maturities of derivatives, days | 30 days | 36 days |