Schedule of Summary of Derivative Hedges (Detail) (USD $)	12 Months Ended
	May 31, 2014
Derivatives Not Designated As Hedging Instruments | Commodity Contracts
Derivative [Line Items]
Notional Amount	$ 24,660,000
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Minimum
Derivative [Line Items]
Maturity Date(s)	2014-06
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date(s)	2015-12
Derivatives Not Designated As Hedging Instruments | Foreign Currency Contracts
Derivative [Line Items]
Notional Amount	6,830,000
Maturity Date(s)	2014-06
Cash Flow Hedges | Commodity Contracts
Derivative [Line Items]
Notional Amount	26,700,000
Cash Flow Hedges | Commodity Contracts | Minimum
Derivative [Line Items]
Maturity Date(s)	2014-06
Cash Flow Hedges | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date(s)	2015-12
Cash Flow Hedges | Interest Rate Contracts
Derivative [Line Items]
Notional Amount	$ 100,000,000
Maturity Date(s)	2014-12