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