Change in Product Warranty Liability (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Product Information [Line Items]
Balance at beginning of period	$ 1,217	$ 1,672
Warranty expenditures for current period	(705)	(966)
Changes in liability related to pre-existing warranties	2
Provision for warranty costs in the period	781	1,011
Balance at end of period	$ 1,295	$ 1,717