Schedule of Gain on Involuntary Conversion (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended		24 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011
Unusual or Infrequent Item [Line Items]
Insurance recoveries recognized	$ 10,437	$ 18,079	$ 28,516
Deductible		(5,000)	(5,000)
Work in process and raw material destroyed		(4,305)	(4,305)
Property and equipment destroyed	(165)	(578)	(743)
Clean-up and other costs	(855)	(603)	(1,458)
Gain on involuntary conversion	$ 9,417	$ 7,593	$ 17,010