Product General Warranty Liability (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Product Liability Contingency [Line Items]
Balance at the beginning of the period	$ 5,174	$ 6,103
Accrual	6,407	5,381
Settlements made in cash or in kind during the period	(5,947)	(6,310)
Balance at the end of the period	$ 5,634	$ 5,174