Performance Shares Granted (Detail) (Performance Shares, USD $)	12 Months Ended
May 31, 2014	May 31, 2013	May 31, 2012
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	59,000	108,000	91,000
Weighted average grant date fair value, per share	$ 33.33	$ 22.08	$ 22.35
Pre-tax stock-based compensation	$ 1,958,000	$ 2,383,000	$ 2,039,000

Unrecognized cost of unvested share-based awards, other than 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

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ 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 (c)(2)(iii)(1)

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

+ Details

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Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

+ Details

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- Details

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