Restructuring (Details) (USD $) In Thousands	3 Months Ended	12 Months Ended
Jul. 31, 2011	Jul. 31, 2010	Apr. 30, 2011	Apr. 30, 2010
Restructuring and related charges
Total expected restructuring charge	$ 235,000		$ 235,000
Beginning Balance	10,198	1,089	1,089	0
Charge to expense	19,563	27,557	101,957	5,711
Cash payments	(7,628)		(30,739)	(752)
Noncash utilization	(10,564)		(62,109)	(3,870)
Ending Balance	11,569		10,198	1,089
Remaining expected restructuring charge	107,769		127,332
Long-Lived Asset Charges [Member]
Restructuring and related charges
Total expected restructuring charge	118,000		118,000
Beginning Balance	0	0	0	0
Charge to expense	9,655		53,569	3,870
Cash payments	0		0	0
Noncash utilization	(9,655)		(53,569)	(3,870)
Ending Balance	0		0	0
Remaining expected restructuring charge	50,906		60,561
Employee Separation [Member]
Restructuring and related charges
Total expected restructuring charge	60,000		60,000
Beginning Balance	10,198	1,089	1,089	0
Charge to expense	5,785		36,010	1,139
Cash payments	(3,505)		(18,361)	(50)
Noncash utilization	(909)		(8,540)	0
Ending Balance	11,569		10,198	1,089
Remaining expected restructuring charge	17,066		22,851
Site Preparation and Equipment Relocation [Member]
Restructuring and related charges
Total expected restructuring charge	23,500		23,500
Beginning Balance	0	0	0	0
Charge to expense	1,988		6,192	407
Cash payments	(1,988)		(6,192)	(407)
Noncash utilization	0		0	0
Ending Balance	0		0	0
Remaining expected restructuring charge	14,913		16,901
Production start-up [Member]
Restructuring and related charges
Total expected restructuring charge	23,000		23,000
Beginning Balance	0	0	0	0
Charge to expense	1,738		5,194	16
Cash payments	(1,738)		(5,194)	(16)
Noncash utilization	0		0	0
Ending Balance	0		0	0
Remaining expected restructuring charge	16,052		17,790
Other Costs [Member]
Restructuring and related charges
Total expected restructuring charge	10,500		10,500
Beginning Balance	0	0	0	0
Charge to expense	397		992	279
Cash payments	(397)		(992)	(279)
Noncash utilization	0		0	0
Ending Balance	0		0	0
Remaining expected restructuring charge	$ 8,832		$ 9,229

Amount expected to be charged against earnings in the current and future periods for the specified restructuring costs, as estimated at the balance sheet date.

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- Definition

Noncash portion of amount charged against earnings in the period for incurred and estimated costs, excluding asset retirement obligations, associated with exit from or disposal of business activities or restructurings pursuant to a program that is planned and controlled by management, and materially changes either the scope of a business undertaken by an entity, or the manner in which that business is conducted.

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- Definition

Remaining restructuring costs expected to be incurred in future periods, as estimated at the balance sheet date.

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- Details

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- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan, excluding costs or losses pertaining to an entity newly acquired in a business combination and to asset retirement obligations.

+ References

+ Details

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- Definition

Reserve increase representing the amount charged against earnings in the period for a specified incurred and estimated type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 146

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- Definition

Amount of cash paid in the period to fully or partially settle a specified, previously accrued type of restructuring cost.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 95-3

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 146

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