Stock-based Compensation Expense Included in the Results of Operations and the Tax Benefit Associated with the Exercise of Stock Options (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2012		Jan. 31, 2011		Jan. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 21,658	[1]	$ 20,511	[1]	$ 26,159	[1]
Tax effect of the exercise of stock options					(96)
Service and support
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	1,065		888		1,618
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	8,203		7,785		10,931
Marketing and selling
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	5,874		6,112		8,406
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 6,516		$ 5,726		$ 5,204

[1] All of equity plan-related compensation expense for the years ended January 31, 2012 and 2011 relates to stock options, stock awards, and the ESPPs. Equity plan-related compensation expense for the year ended January 31, 2010 includes $25,657 relating to stock options, stock awards, and the ESPPs and $502 relating to the amortization of expense associated with stock issued to the founders of a company we acquired during the year ended January 31, 2008.