Percentage of Net Product and Engineering Revenue from Major Customers (Detail) - Sales Revenue, Net - Largest customers	3 Months Ended		6 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	63.00%	61.00%	63.00%	62.00%
L-3
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	10.00%		10.00%
Philips
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	14.00%	13.00%	13.00%	13.00%
Siemens AG
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	11.00%	13.00%	12.00%	14.00%
Toshiba
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	11.00%	11.00%	10.00%	11.00%