Employee Stock and Savings Plans - Stock Compensation Expense Recognized (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	$ 29,350	$ 23,697	$ 21,658
Tax effect of the exercise of stock options	386	266	0
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	1,992	1,529	1,065
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	11,182	9,206	8,203
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	7,777	6,654	5,874
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	$ 8,399	$ 6,308	$ 6,516