Stock Options Outstanding (Detail) (USD $)	12 Months Ended
May 31, 2012
Range Of Exercise Prices, $16.04 - $29.38
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Shares outstanding	818,763
Weighted-average remaining term in years, Options outstanding	6 years 8 months 19 days
Weighted-average exercise price, Options outstanding	$ 25.32
Shares exercisable	323,633
Weighted-average remaining term in years, Options exercisable	3 years 8 months 16 days
Weighted-average exercise price, Options exercisable	$ 21.09
Range of Exercise Prices, minimum	$ 16.04
Range of Exercise Prices, maximum	$ 29.38
Range Of Exercise Prices, $33.57 - $48.60
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Shares outstanding	800,257
Weighted-average remaining term in years, Options outstanding	6 years 8 months 1 day
Weighted-average exercise price, Options outstanding	$ 39.68
Shares exercisable	346,447
Weighted-average remaining term in years, Options exercisable	5 years 1 month 13 days
Weighted-average exercise price, Options exercisable	$ 41.06
Range of Exercise Prices, minimum	$ 33.57
Range of Exercise Prices, maximum	$ 48.60
Range Of Exercise Prices, $50.63 - $70.18
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Shares outstanding	526,550
Weighted-average remaining term in years, Options outstanding	4 years 22 days
Weighted-average exercise price, Options outstanding	$ 57.37
Shares exercisable	490,340
Weighted-average remaining term in years, Options exercisable	3 years 11 months 27 days
Weighted-average exercise price, Options exercisable	$ 57.86
Range of Exercise Prices, minimum	$ 50.63
Range of Exercise Prices, maximum	$ 70.18

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Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

+ References

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- Definition

Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-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 (g)

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

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- Definition

The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-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 (c)(iii)

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

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- Definition

The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ 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)(1)(i)-(ii)

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

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a, b)

-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.

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- Definition

The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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- Definition

Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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- Definition

The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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