Employee Stock and Savings Plans - Stock Compensation Expense Recognized (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 6,306,000	$ 5,829,000	$ 11,453,000	$ 11,509,000
Employee Stock Purchase Plan Purchase Shares And Contributions By Eligible Participants Description	We have an employee stock purchase plan (ESPP) for U.S. employees and an ESPP for certain foreign subsidiary employees. The ESPPs provide for six month offerings commencing on January 1 and July 1 of each year with purchases on June 30 and December 31 of each year. Each eligible employee may purchase up to six thousand shares of stock on each purchase date (but no more than an annual offering date total fair market value of $25) at prices no less than 85% of the lesser of the fair market value of the shares on the offering date or on the purchase date.
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	368,000	237,000	687,000	504,000
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	2,215,000	1,975,000	4,332,000	4,114,000
Marketing and selling
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	1,625,000	1,413,000	3,174,000	3,028,000
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	2,098,000	2,204,000	3,260,000	3,863,000
Omnibus Incentive Plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period			4 years
Share Based Compensation Arrangement By Share Based Payment Award Expiry Period From Date Of Grant			10 years
Employee Stock Purchase Plans
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee Stock Purchase Plan Maximum Number Of Shares That May Be Purchased By Eligible Participants (in shares)			6,000
Maximum Share Value Authorized For Purchase Under Employee Stock Purchase Plan			$ 25,000
Eligible employee stock purchase price			85.00%
Share Based Compensation Arrangement By Share Based Payment Award Employee Stock Purchase Plan Offering Term			6 months