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