Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Aug. 31, 2014	Aug. 31, 2013
Income Tax [Line Items]
Effective income tax rate	29.20%	27.40%
Federal statutory rate	35.00%	35.00%
Unrecognized tax benefits	$ 15.7
Unrecognized tax benefits that would impact effective tax rate, if recognized	15.0
Accrued interest and penalties related to unrecognized tax benefits	$ 5.2

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

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-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(2))

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-Name Regulation S-X (SX)

-Number 210

-Section 08

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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-Publisher FASB

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-Paragraph 1

-Subparagraph (SAB TOPIC 6.I)

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

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-Subparagraph (c)

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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