Investments - Effect of Derivative Instruments Not Designated as Hedging Instruments on Condensed Consolidated Statements of Operations (Detail) (Derivatives not designated as hedging instruments, Foreign currency derivative contracts, Other expense, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Derivatives not designated as hedging instruments | Foreign currency derivative contracts | Other expense
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on Derivative Instruments Recognized in Income	$ (3,068)	$ 4,523	$ (2,964)	$ 2,468