Earning Per Share - Reconciliation of Numerators and Denominators for Basic and Diluted EPS Computations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Earnings Per Share [Abstract]
Net earnings for basic and diluted EPS	$ 94,610	$ 63,179	$ 284,968	$ 236,514
Weighted-average shares for basic EPS	128,004	126,737	127,716	126,697
Incremental shares based upon the assumed exercise of stock options and unvested restricted stock units	970	1,165	1,013	1,217
Weighted-average shares for diluted EPS	128,974	127,902	128,729	127,914

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

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-Name Emerging Issues Task Force (EITF)

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+ Details

- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References+ Details

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References+ Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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-Glossary Weighted-Average Number of Common Shares Outstanding

-URI http://asc.fasb.org/extlink&oid=6528421

+ Details