Percentage of Net Product and Engineering Revenue from Major Customers (Detail) - Sales Revenue, Net - Largest customers	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Dec. 31, 2015	Jan. 31, 2015
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	61.00%	62.00%	62.00%		63.00%
Philips
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	13.00%	13.00%	13.00%	12.00%
L-3
Concentration Risk [Line Items]
Percentage of net product and engineering revenue		13.00%		11.00%
Toshiba
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	11.00%		11.00%	12.00%
Siemens AG
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	13.00%	10.00%	14.00%	12.00%