Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net foreign currency exchange (gain) loss	$ 4,924	$ 7,600	$ 2,872	$ 2,100
Notional amount of derivative financial instruments outstanding	$ 510,335	$ 600,000	$ 546,000	$ 681,000
Average maturities of derivatives, days	24 days	35 days	31 days	35 days