Non-Qualified Stock Options Granted (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
May 31, 2014	May 31, 2013	May 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	130	1,034	600
Weighted average exercise price, per share	$ 32.21	$ 20.83	$ 21.15
Weighted average grant date fair value, per share	$ 12.92	$ 7.71	$ 8.25
Pre-tax stock-based compensation	$ 1,539	$ 7,165	$ 4,456

Unrecognized cost of unvested options awarded to employees as compensation.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ 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 (d)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

+ References

No definition available.

+ Details

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