Employee Stock and Savings Plans - Stock Compensation Expense Recognized (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 7,277	$ 6,306	$ 13,843	$ 11,453
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	458	368	918	687
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	2,543	2,215	5,153	4,332
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	1,771	1,625	3,653	3,174
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 2,505	$ 2,098	$ 4,119	$ 3,260
Omnibus Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award requisite service period			4 years
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]
Maximum number of shares that may be purchased by eligible participants (in shares)			6,000
Eligible employee stock purchase price			85.00%
Employee stock purchase plan offering term			6 months