Schedule of Summary of Derivative Hedges (Detail) - May. 31, 2015 - USD ($) $ in Thousands	Total
Commodity Contracts | Derivatives Not Designated As Hedging Instruments
Derivative [Line Items]
Notional Amount	$ 33,564
Commodity Contracts | Derivatives Not Designated As Hedging Instruments | Minimum
Derivative [Line Items]
Maturity Date	2015-06
Commodity Contracts | Derivatives Not Designated As Hedging Instruments | Maximum
Derivative [Line Items]
Maturity Date	2016-11
Cash Flow Hedges | Commodity Contracts
Derivative [Line Items]
Notional Amount	$ 102,129
Cash Flow Hedges | Commodity Contracts | Minimum
Derivative [Line Items]
Maturity Date	2015-06
Cash Flow Hedges | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date	2016-12
Cash Flow Hedges | Interest Rate Contracts
Derivative [Line Items]
Notional Amount	$ 16,809
Maturity Date	2019-09
Cash Flow Hedges | Foreign Currency Contracts
Derivative [Line Items]
Notional Amount	$ 570
Cash Flow Hedges | Foreign Currency Contracts | Maximum
Derivative [Line Items]
Maturity Date	2015-06