Schedule of Summary of Derivative Hedges (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012
Derivatives Not Designated As Hedging Instruments | Commodity Contracts
Derivative [Line Items]
Notional Amount	49,888
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Minimum
Derivative [Line Items]
Maturity Date(s)	2012-09
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date(s)	2013-12
Derivatives Not Designated As Hedging Instruments | Foreign Exchange Contracts
Derivative [Line Items]
Notional Amount	63,740
Maturity Date(s)	2012-11
Cash Flow Hedges | Commodity Contracts | Minimum
Derivative [Line Items]
Notional Amount	3,983
Maturity Date(s)	2012-09
Cash Flow Hedges | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date(s)	2013-12
Cash Flow Hedges | Interest Rate Contracts
Derivative [Line Items]
Notional Amount	100,000
Maturity Date(s)	2014-12