Schedule of Financial Assets And Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2013	May 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 3,183	$ 761
Liabilities	6,313	9,774
Derivative Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,183	761
Liabilities	6,313	9,774
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,183	761
Liabilities	6,313	9,774
Significant Other Observable Inputs (Level 2) | Derivative Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,183	761
Liabilities	$ 6,313	$ 9,774