Stock-based Compensation - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Apr. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of ordinary shares	$ 73.15
Stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost, stock options	$ 11.3
Weighted average recognition period	2 years 5 months 27 days
Restricted stock units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost, restricted stock units	46.1
Weighted average recognition period	2 years 8 months 19 days
Aggregate intrinsic value of unvested restricted stock units	$ 133.2

Closing market price of ordinary shares on NASDAQ on the last day of reporting period.

No definition available.

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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.

+ 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

+ Details

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

No definition available.

+ Details

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

No definition available.

+ Details

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- Definition

Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

+ References

No definition available.

+ Details

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- Details

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