Restructuring (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011	Apr. 30, 2011	Oct. 31, 2011
Restructuring and related charges
Total expected restructuring charge	$ 245,000		$ 245,000			$ 235,000
Beginning Balance			10,198	1,089	1,089
Charge to expense	25,571	25,265	67,294	73,239	101,957
Cash payments			(31,241)		(30,739)
Noncash utilization			(36,078)		(62,109)
Ending Balance	10,173		10,173		10,198
Remaining expected restructuring charge	70,038		70,038
Long-Lived Asset Charges [Member]
Restructuring and related charges
Total expected restructuring charge	105,000		105,000
Beginning Balance			0	0	0
Charge to expense			29,136		53,569
Cash payments			0		0
Noncash utilization			(29,136)		(53,569)
Ending Balance	0		0		0
Remaining expected restructuring charge	18,425		18,425
Employee Separation [Member]
Restructuring and related charges
Total expected restructuring charge	71,000		71,000
Beginning Balance			10,198	1,089	1,089
Charge to expense			18,551		36,010
Cash payments			(11,634)		(18,361)
Noncash utilization			(6,942)		(8,540)
Ending Balance	10,173		10,173		10,198
Remaining expected restructuring charge	15,300		15,300
Site Preparation and Equipment Relocation [Member]
Restructuring and related charges
Total expected restructuring charge	31,000		31,000
Beginning Balance			0	0	0
Charge to expense			8,883		6,192
Cash payments			(8,883)		(6,192)
Noncash utilization			0		0
Ending Balance	0		0		0
Remaining expected restructuring charge	15,518		15,518
Production start-up [Member]
Restructuring and related charges
Total expected restructuring charge	26,000		26,000
Beginning Balance			0	0	0
Charge to expense			9,241		5,194
Cash payments			(9,241)		(5,194)
Noncash utilization			0		0
Ending Balance	0		0		0
Remaining expected restructuring charge	11,549		11,549
Other Costs [Member]
Restructuring and related charges
Total expected restructuring charge	12,000		12,000
Beginning Balance			0	0	0
Charge to expense			1,483		992
Cash payments			(1,483)		(992)
Noncash utilization			0		0
Ending Balance	0		0		0
Remaining expected restructuring charge	$ 9,246		$ 9,246