Employee Stock and Savings Plans Stock Compensation Expense Recognized (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	$ 35,807	$ 29,350	$ 23,697
Tax effect of the exercise of stock options	280	386	266
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	2,304	1,992	1,529
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	14,027	11,182	9,206
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	9,103	7,777	6,654
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	10,373	8,399	6,308
Restricted Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized	68,648
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	1 year 4 months 24 days
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized	$ 1,667
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	8 months 12 days

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

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-Publisher SEC

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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