Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency loss	$ 4.3	$ (9.0)	$ (18.8)
Notional amount of derivative financial instruments outstanding	$ 600.0	$ 600.0	$ 700.0
Average maturities of derivatives, days	29 days	30 days	32 days