Deferred Tax Assets and Liabilities Classified in Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	May 31, 2012	May 31, 2011
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred income taxes, current assets	$ 20,906	$ 28,297
Deferred income taxes, other assets		2,006
Other accrued items, Current liabilities	(39)
Deferred income taxes, noncurrent liabilities	(73,099)	(83,981)
Net deferred tax liabilities	$ (52,232)	$ (53,678)

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards expected to be realized or consumed within one year or operating cycle, if longer.

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Amount after allocation of valuation allowances of noncurrent deferred tax asset attributable to deductible temporary differences and carryforwards. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences, net of deferred tax asset attributable to deductible temporary differences and carryforwards net of valuation allowances expected to be realized or consumed within one year or operating cycle, if longer.

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- Definition

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