Schedule of Derivatives Designated as Cash Flow Hedging Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011
Derivative [Line Items]
Income (Loss) Recognized in OCI (Effective Portion)	$ 147	$ (450)	$ (31)	$ (2,296)
Income (Loss) Reclassified from Accumulated OCI (Effective Portion)	(406)	(1,214)	(1,808)	(263)
Income (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing
Interest Rate Contracts
Derivative [Line Items]
Income (Loss) Recognized in OCI (Effective Portion)	117	257	(489)	(1,873)
Interest Rate Contracts | Interest Expense
Derivative [Line Items]
Income (Loss) Reclassified from Accumulated OCI (Effective Portion)	(665)	(928)	(1,648)	(1,998)
Income (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing
Commodity Contracts
Derivative [Line Items]
Income (Loss) Recognized in OCI (Effective Portion)	30	(707)	458	(423)
Commodity Contracts | Cost Of Goods Sold
Derivative [Line Items]
Income (Loss) Reclassified from Accumulated OCI (Effective Portion)	259	(286)	(160)	1,735
Income (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing