Derivative Instruments and Hedging Activities - Schedule of Fair Value of Derivative Instruments (Detail) - USD ($) $ in Thousands	Aug. 31, 2018	May 31, 2018
Derivative [Line Items]
Asset Derivatives at Fair Value	$ 5,144	$ 11,423
Liability Derivatives at Fair Value	1,569	846
Designated as Hedging Instrument
Derivative [Line Items]
Asset Derivatives at Fair Value	3,133	6,453
Liability Derivatives at Fair Value	215
Designated as Hedging Instrument | Commodity Contracts | Other Liabilities
Derivative [Line Items]
Liability Derivatives at Fair Value	36
Designated as Hedging Instrument | Commodity Contracts | Receivables
Derivative [Line Items]
Asset Derivatives at Fair Value	3,133	6,385
Designated as Hedging Instrument | Commodity Contracts | Other Assets
Derivative [Line Items]
Asset Derivatives at Fair Value		68
Designated as Hedging Instrument | Commodity Contracts | Accounts Payable
Derivative [Line Items]
Liability Derivatives at Fair Value	179
Derivatives Not Designated As Hedging Instruments
Derivative [Line Items]
Asset Derivatives at Fair Value	2,011	4,970
Liability Derivatives at Fair Value	1,354	846
Derivatives Not Designated As Hedging Instruments | Commodity Contracts
Derivative [Line Items]
Asset Derivatives at Fair Value	2,006	4,970
Liability Derivatives at Fair Value	1,354	771
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Other Liabilities
Derivative [Line Items]
Liability Derivatives at Fair Value	438	158
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Receivables
Derivative [Line Items]
Asset Derivatives at Fair Value	1,789	4,749
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Other Assets
Derivative [Line Items]
Asset Derivatives at Fair Value	217	221
Derivatives Not Designated As Hedging Instruments | Commodity Contracts | Accounts Payable
Derivative [Line Items]
Liability Derivatives at Fair Value	916	613
Derivatives Not Designated As Hedging Instruments | Foreign Currency Contracts | Receivables
Derivative [Line Items]
Asset Derivatives at Fair Value	$ 5
Derivatives Not Designated As Hedging Instruments | Foreign Currency Contracts | Accounts Payable
Derivative [Line Items]
Liability Derivatives at Fair Value		$ 75