Risks and Uncertainties - Additional Information (Detail)	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011		Jul. 31, 2010
Ten largest customers
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	68.00%	64.00%		66.00%
Philips
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	14.00%	13.00%		15.00%
Percentage of net accounts receivable	13.00%	17.00%
General Electric Corporation
Concentration Risk [Line Items]
Percentage of net accounts receivable	10.00%	12.00%
L-3
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	12.00%		[1]		[1]
Percentage of net accounts receivable	18.00%

[1] Total net revenue was less than 10% in this fiscal year.