Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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Percentage of fair value of reporting unit in excess of carrying amount.

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Price of a single share of a number of saleable stocks of a company.

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Goodwill (Details)			3 Months Ended	9 Months Ended
Goodwill (Details)	Apr. 30, 2020 USD ($) reporting_unit	Aug. 01, 2019 USD ($) reporting_unit $ / shares	Apr. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)
Goodwill [Roll Forward]
Beginning balance		$ 310,489,000		$ 310,489,000
Ending balance	$ 335,477,000		$ 335,477,000	335,477,000
Number of reporting units \| reporting_unit	2	2
Common Stock
Goodwill [Roll Forward]
Common stock price (in dollars per share) \| $ / shares		$ 29.54
Solacom
Goodwill [Roll Forward]
Change resulting from acquisitions, adjustments				(420,000)
GD NG-911 business
Goodwill [Roll Forward]
Change resulting from acquisitions				4,556,000
CGC Technology
Goodwill [Roll Forward]
Beginning balance			15,950,000
Change resulting from acquisitions, adjustments			4,902,000
Change resulting from acquisitions				20,852,000
Ending balance	$ 20,852,000		20,852,000	20,852,000
Commercial Solutions Segment
Goodwill [Roll Forward]
Beginning balance		$ 251,296,000		251,296,000
Ending balance	255,432,000		255,432,000	255,432,000
Reporting unit, percentage of fair value in excess of carrying amount		29.00%
Commercial Solutions Segment \| Solacom
Goodwill [Roll Forward]
Change resulting from acquisitions, adjustments				(420,000)
Commercial Solutions Segment \| GD NG-911 business
Goodwill [Roll Forward]
Change resulting from acquisitions				4,556,000
Commercial Solutions Segment \| CGC Technology
Goodwill [Roll Forward]
Change resulting from acquisitions				0
Government Solutions Segment
Goodwill [Roll Forward]
Beginning balance		$ 59,193,000		59,193,000
Ending balance	$ 80,045,000		$ 80,045,000	80,045,000
Reporting unit, percentage of fair value in excess of carrying amount		122.20%
Government Solutions Segment \| Solacom
Goodwill [Roll Forward]
Change resulting from acquisitions, adjustments				0
Government Solutions Segment \| GD NG-911 business
Goodwill [Roll Forward]
Change resulting from acquisitions				0
Government Solutions Segment \| CGC Technology
Goodwill [Roll Forward]
Change resulting from acquisitions				$ 20,852,000