Non-Qualified Stock Options Granted (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
May 31, 2012	May 31, 2011	May 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	600	2,437	993
Weighted average exercise price, per share	$ 21.15	$ 12.27	$ 13.36
Weighted average grant date fair value, per share	$ 7.42	$ 4.88	$ 4.85
Pre-tax stock-based compensation	$ 4,456	$ 9,715	$ 3,968

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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

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