Schedule of Derivatives Designated as Cash Flow Hedging Instruments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011
Derivative [Line Items]
Income (Loss) Recognized in Other Comprehensive Income (Effective Portion)	$ (2,611)	$ (4,323)
Income (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	(2,039)	(3,918)
Income (Loss) (Ineffective Portion) Excluded from Effectiveness Testing
Interest Rate Contracts
Derivative [Line Items]
Income (Loss) Recognized in Other Comprehensive Income (Effective Portion)	(2,398)	(5,724)
Interest Rate Contracts | Interest Expense
Derivative [Line Items]
Income (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	(4,032)	(4,043)
Income (Loss) (Ineffective Portion) Excluded from Effectiveness Testing
Commodity Contracts
Derivative [Line Items]
Income (Loss) Recognized in Other Comprehensive Income (Effective Portion)	(213)	1,401
Commodity Contracts | Cost Of Goods Sold
Derivative [Line Items]
Income (Loss) Reclassified from Accumulated Other Comprehensive Income (Effective Portion)	1,993	125
Income (Loss) (Ineffective Portion) Excluded from Effectiveness Testing