Schedule of Derivatives Designated as Cash Flow Hedging Instruments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Aug. 31, 2013	Aug. 31, 2012
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ 3,441	$ (178)
Gain (Loss) Reclassified from Accumulated OCI (Effective Portion)	(1,379)	(1,402)
Gain (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing
Interest Rate Contracts
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	(203)	(606)
Interest Rate Contracts \| Interest Expense
Derivative [Line Items]
Gain (Loss) Reclassified from Accumulated OCI (Effective Portion)	(1,063)	(983)
Gain (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing
Commodity Contracts
Derivative [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	3,644	428
Commodity Contracts \| Cost Of Goods Sold
Derivative [Line Items]
Gain (Loss) Reclassified from Accumulated OCI (Effective Portion)	(316)	(419)
Gain (Loss) (Ineffective Portion) and Excluded from Effectiveness Testing

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4D

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624177-113959

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1),(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

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