Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013
Income Tax [Line Items]
Effective income tax rate	30.20%	(29.90%)	29.60%	28.40%
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Unrecognized tax benefits	$ 14.8us-gaap_UnrecognizedTaxBenefits		$ 14.8us-gaap_UnrecognizedTaxBenefits
Unrecognized tax benefits that would impact effective tax rate, if recognized	14.1		14.1
Accrued interest and penalties related to unrecognized tax benefits	$ 4.7		$ 4.7

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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

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

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

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-Glossary Unrecognized Tax Benefit

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

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