Risks and Uncertainties - Additional Information (Detail)	12 Months Ended
	Jul. 31, 2013 Customer	Jul. 31, 2012 Customer	Jul. 31, 2011 Customer
Concentration Risk [Line Items]
Number of customer accounted for more than ten percent sales	3	3	3
Ten largest customers
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	68.00%	68.00%	64.00%
Philips
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	15.00%	14.00%	13.00%
Percentage of net accounts receivable	18.00%	13.00%
General Electric Corporation
Concentration Risk [Line Items]
Percentage of net accounts receivable	7.00%	10.00%
L-3
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	12.00%	12.00%		[1]
Percentage of net accounts receivable	16.00%	18.00%

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