Employee Stock and Savings Plans Stock Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	$ 40,497	$ 35,807	$ 29,350
Tax effect of the exercise of stock options	217	280	386
Cost of goods sold
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	2,607	2,304	1,992
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	16,207	14,027	11,182
Selling and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	9,623	9,103	7,777
General and administration
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Equity plan-related compensation expense	12,060	$ 10,373	$ 8,399
Restricted Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized	$ 73,099
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	1 year 4 months 24 days
Employee Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized	$ 386
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition	4 months 24 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 S99
-Paragraph 1
-Subparagraph (SAB TOPIC 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section F

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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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- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
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