Derivative Instruments (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency exchange loss	$ (6,900,000)	$ 1,900,000	$ (13,600,000)	$ 9,800,000
Notional amount of derivative financial instruments outstanding	$ 1,400,000,000	$ 1,800,000,000
Average maturities of derivatives, days	30 days	28 days