Schedule of Summary of Derivative Hedges (Detail) $ in Thousands	3 Months Ended
	Aug. 31, 2015 USD ($)
Commodity Contracts | Derivatives Not Designated As Hedging Instruments
Derivative [Line Items]
Notional Amount	$ 31,275
Commodity Contracts | Derivatives Not Designated As Hedging Instruments | Minimum
Derivative [Line Items]
Maturity Date	2015-09
Commodity Contracts | Derivatives Not Designated As Hedging Instruments | Maximum
Derivative [Line Items]
Maturity Date	2017-02
Foreign Currency Contracts | Derivatives Not Designated As Hedging Instruments
Derivative [Line Items]
Notional Amount	$ 774
Maturity Date	2015-11
Cash Flow Hedges | Commodity Contracts
Derivative [Line Items]
Notional Amount	$ 78,081
Cash Flow Hedges | Commodity Contracts | Minimum
Derivative [Line Items]
Maturity Date	2015-09
Cash Flow Hedges | Commodity Contracts | Maximum
Derivative [Line Items]
Maturity Date	2016-12
Cash Flow Hedges | Interest Rate Contracts
Derivative [Line Items]
Notional Amount	$ 17,153
Maturity Date	2019-09