Investments - Fair Value of Outstanding Derivative Instruments (Detail) (Derivatives not designated as hedging instruments, Foreign currency derivative contracts, USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Jan. 31, 2014
Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 10,611	$ 1,598
Accounts payable, accrued expenses and other liabilities
Derivatives, Fair Value [Line Items]
Derivative Liabilities	$ 5,694	$ 1,801