Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency gain	$ 9.0	$ 18.8	$ 17.2
Notional amount of derivative financial instruments outstanding	$ 600.0	$ 700.0
Average maturities of derivatives, days	30 days	32 days