Fair Values and Balance Sheet Presentation of Derivative Instruments (Detail) (USD $) In Thousands	Jul. 31, 2011	Jan. 31, 2011
Asset Derivatives
Asset derivatives	$ 1,589	$ 1,700
Liability Derivatives
Liability derivatives	(558)	(874)
Derivatives not designated as hedging instruments
Liability Derivatives
Liability derivatives	(533)	(460)
Derivatives not designated as hedging instruments | Other receivables
Asset Derivatives
Asset derivatives	1,589	1,125
Derivatives designated as hedging instruments | Cash flow forwards
Liability Derivatives
Liability derivatives	(25)	(414)
Derivatives designated as hedging instruments | Cash flow forwards | Other receivables
Asset Derivatives
Asset derivatives		$ 575