Customer and Geographic Information (Details) - USD ($)	3 Months Ended
Oct. 31, 2017	Oct. 31, 2016
Revenues from External Customers
Entity wide revenue percentage by major customer type	100.00%	100.00%
Major customer
Revenues from External Customers
Minimum percentage of consolidated net sales sold to one customer or individual country requiring additional and separate disclosure	10.00%	10.00%
U.S. government
Revenues from External Customers
Entity wide revenue percentage by major customer type	32.40%	35.30%
Commercial (United States)
Revenues from External Customers
Entity wide revenue percentage by major customer type	44.30%	36.80%
Total United States
Revenues from External Customers
Entity wide revenue percentage by major customer type	76.70%	72.10%
International
Revenues from External Customers
Entity wide revenue percentage by major customer type	23.30%	27.90%
Revenue generated from external customers	$ 28,315,000	$ 37,833,000
Verizon Communications Inc. \| Major customer \| Sales Revenue, Net
Revenues from External Customers
Percentage of revenue generated from external customer type	11.70%

Percentage of revenue generated from a single external customer type.

No definition available.

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- Definition

The minimum percentage of consolidated net sales that, if made to one customer or country, would require additional and separate disclosure.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

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

+ Details

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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