Derivative Financial Instruments (Details) (USD $) In Thousands	12 Months Ended
Apr. 30, 2011	Apr. 30, 2010
Gains and losses recognized in cost of products sold on derivatives not designated as qualified hedging instruments
Losses recognized in cost of products sold (derivatives not designated as hedging instruments)	$ 7,284	$ 9,618
Derivative Financial Instruments (Textuals)
Cash margin accounts related to derivative instruments recognized	12,292	5,714
Deferred pretax gains included in accumulated other comprehensive income (loss)	9,430	3,128
Tax impact related to deferred gains on cash flow hedges included in accumulated other comprehensive income (loss)	3,430	1,134
Other Current Assets [Member]
Fair value of derivative instruments [Line Items]
Derivative asset designated as hedging instrument	8,831	1,874
Derivative asset not designated as hedging instrument	10,204	2,414
Total derivatives instruments, Other Current Assets	19,035	4,288
Other Current Assets [Member] \| Commodity contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative asset designated as hedging instrument	3,408	1,874
Derivative asset not designated as hedging instrument	9,887	2,414
Other Current Assets [Member] \| Interest rate contract [Member]
Fair value of derivative instruments [Line Items]
Derivative asset designated as hedging instrument	5,423	0
Other Current Assets [Member] \| Foreign currency exchange contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative asset not designated as hedging instrument	317	0
Other Current Liabilities [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	0	9
Derivative liability not designated as hedging instrument	8,636	1,429
Total derivative instruments, Liabilities	8,636	1,438
Other Current Liabilities [Member] \| Commodity contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	0	9
Derivative liability not designated as hedging instrument	5,432	599
Other Current Liabilities [Member] \| Interest rate contract [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	0	0
Other Current Liabilities [Member] \| Foreign currency exchange contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative liability not designated as hedging instrument	3,204	830
Other Noncurrent Liabilities [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	1,384
Derivative liability not designated as hedging instrument	0
Total derivative instruments, Liabilities	1,384
Other Noncurrent Liabilities [Member] \| Commodity contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	0
Derivative liability not designated as hedging instrument	0
Other Noncurrent Liabilities [Member] \| Interest rate contract [Member]
Fair value of derivative instruments [Line Items]
Derivative liability designated as hedging instrument	1,384
Other Noncurrent Liabilities [Member] \| Foreign currency exchange contracts [Member]
Fair value of derivative instruments [Line Items]
Derivative liability not designated as hedging instrument	0
Commodity contracts [Member]
Gains and losses recognized in cost of products sold on derivatives not designated as qualified hedging instruments
Losses recognized in cost of products sold (derivatives not designated as hedging instruments)	3,994	2,384
Outstanding derivative contracts
Gross contract notional amount	869,107	323,351
Interest rate contract [Member]
Outstanding derivative contracts
Gross contract notional amount	376,000	0
Foreign currency exchange contracts [Member]
Gains and losses recognized in cost of products sold on derivatives not designated as qualified hedging instruments
Losses recognized in cost of products sold (derivatives not designated as hedging instruments)	3,290	7,234
Outstanding derivative contracts
Gross contract notional amount	73,158	45,295
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains recognized in other comprehensive income (effective portion)	21,082	6,029
Gains reclassified from accumulated other comprehensive income (loss) to cost of products sold (effective portion)	14,780	5,395
Change in accumulated other comprehensive income (loss)	6,302	634
Gains recognized in cost of products sold (ineffective portion)	$ 611	$ 200

Amount of gain or loss on cash flow hedging derivatives deferred in accumulated other comprehensive income or loss as of the balance sheet date.

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Tax impact related to deferred gains or losses on cash flow hedges included in accumulated other comprehensive loss.

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Fair value of a derivative asset (or nonderivative instrument) that is designated and qualifies as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 205G

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44C
-Subparagraph a
-Clause 1

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Fair value of a derivative asset that is not designated or qualifying as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The income statement location of the effective portion of net gain or loss reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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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.

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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.

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Net gain (loss) included in earnings for the period from the net change in fair value of derivative instrument not designated as hedging instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 45
-Subparagraph b(1)(b)

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Fair value of a derivative liability (or nonderivative instrument) that is designated and qualifies as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Fair value of a derivative liability that is not designated or qualifying as a hedging instrument, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

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Aggregate notional amount of all derivatives. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

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- Definition

Pre tax change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges, net of reclassifications into earnings during the period. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk. Includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 14, 17, 20, 24, 26

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 14, 17, 20, 26

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 45
-Subparagraph b(1)

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 31, 46

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 24
-Subparagraph b

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 46

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