Employee Stock and Savings Plans - Stock Compensation Expense Recognized (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	$ 23,697	$ 21,658	$ 20,511
Stock-based compensation	23,697	21,658	20,511
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	266	0	0
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	1,529	1,065	888
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	9,206	8,203	7,785
Selling and Marketing Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	6,654	5,874	6,112
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated Share-based Compensation Expense	$ 6,308	$ 6,516	$ 5,726
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	6
Eligible employee stock purchase price	85.00%