Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency exchange gain (loss)	$ 0.3	$ (1.2)	$ (22.4)	$ (2.0)
Notional amount of derivative financial instruments outstanding	$ 900.0	$ 700.0	$ 1,000.0	$ 600.0
Average maturities of derivatives, days	28 days	33 days	33 days	32 days