Condensed consolidating statement of operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Net sales	$ 647,003	$ 621,813	$ 621,064
Cost of products sold	601,256	596,510	562,066
Gross profit	45,747	25,303	58,998
Selling, general and administrative	73,057	76,420	79,415
Restructuring charges	3,216
Interest	34,835	47,583	52,240
Loss on debt retirements		29,619
Other income	(73,833)	(21,512)	(10,666)
TOTAL EXPENSES	37,275	132,110	120,989
Income (loss) before the following items	8,472	(106,807)	(61,991)
Income taxes (benefit)	996	(41,894)	(23,138)
Net income (loss) before equity in earnings (loss) of subsidiaries	7,476	(64,913)	(38,853)
NET INCOME (LOSS)	7,476	(64,913)	(38,853)
Parent Company
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Selling, general and administrative	9,349	8,810	14,973
Interest	68,291	66,101	53,114
Loss on debt retirements		29,619
Other income	(56)	(200)	(39)
Intercompany other income	(3,500)	(3,500)	(3,500)
TOTAL EXPENSES	74,084	100,830	64,548
Income (loss) before the following items	(74,084)	(100,830)	(64,548)
Income taxes (benefit)	(27,345)	(37,475)	(21,247)
Net income (loss) before equity in earnings (loss) of subsidiaries	(46,739)	(63,355)	(43,301)
Equity in earnings (loss) of subsidiaries	54,215	(1,558)	4,448
NET INCOME (LOSS)	7,476	(64,913)	(38,853)
Guarantor Subsidiaries
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Net sales	647,003	621,813	621,064
Cost of products sold	601,256	596,510	562,066
Gross profit	45,747	25,303	58,998
Selling, general and administrative	63,708	67,610	64,442
Restructuring charges	3,216
Interest			2,626
Other income	(73,777)	(21,312)	(10,627)
Intercompany other income	(29,956)	(15,018)
TOTAL EXPENSES	(36,809)	31,280	56,441
Income (loss) before the following items	82,556	(5,977)	2,557
Income taxes (benefit)	28,341	(4,419)	(1,891)
Net income (loss) before equity in earnings (loss) of subsidiaries	54,215	(1,558)	4,448
NET INCOME (LOSS)	54,215	(1,558)	4,448
Consolidation, Eliminations
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Interest	(33,456)	(18,518)	(3,500)
Intercompany other income	33,456	18,518	3,500
Equity in earnings (loss) of subsidiaries	(54,215)	1,558	(4,448)
NET INCOME (LOSS)	$ (54,215)	$ 1,558	$ (4,448)