Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Oct. 31, 2011 Contract	Oct. 31, 2010 Contract
Derivative [Line Items]
Number of new foreign currency forward contracts entered during period	1,034	1,031
Number of new foreign currency forward contracts outstanding	33	37
Notional amount of foreign currency derivatives entered into during period outstanding	$ 112,952	$ 176,982
Cash Flow Hedging
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	65	46
Cash Flow Hedging | Cash flow forwards | Other income (expense)
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivatives (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$ 65	$ 46