Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Aug. 31, 2012	Aug. 31, 2011
Income Tax Disclosure [Line Items]
Effective income tax rate	63.20%	34.60%
Increase in income tax benefit due to reduction of UK statutory corporate tax rate	$ 4.0	$ 7.0

The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to total foreign income tax expense or benefit. The foreign income tax expense or benefit difference represents the income tax expense or benefit at applicable domestic statutory income tax rates applied to foreign earnings or loss for the period versus the foreign income tax expense or benefit calculated by applying the appropriate foreign tax rates.

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