For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of Net Product and Engineering Revenue from Major Customers (Parenthetical) (Detail) - Sales Revenue, Net - Largest customers	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	61.00%	61.00%	64.00%
Toshiba
Concentration Risk [Line Items]
Percentage of net product and engineering revenue		11.00%	11.00%
Toshiba \| Maximum
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	10.00%
L-3
Concentration Risk [Line Items]
Percentage of net product and engineering revenue			13.00%
L-3 \| Maximum
Concentration Risk [Line Items]
Percentage of net product and engineering revenue	10.00%	10.00%