Derivative Instruments (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency exchange (gain) loss	$ (3,300,000)	$ (3,600,000)	$ 5,500,000	$ (20,500,000)
Notional amount of derivative financial instruments outstanding	$ 600,000,000	$ 2,000,000,000
Average maturities of derivatives, days	35 days	29 days