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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_ReportingUnitPercentageOfFairValueInExcessOfCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmtl_SolacomTechnologiesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmtl_GDNG911BusinessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cmtl_CGCTechnologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cmtl_CommercialSolutionsSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cmtl_GovernmentSolutionsSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Goodwill (Details)	12 Months Ended
Goodwill (Details)	Jul. 31, 2020 USD ($) operating_segment	Sep. 24, 2020 $ / shares	Aug. 01, 2020 $ / shares
Goodwill [Roll Forward]
Balance as of July 31, 2019	$ 310,489,000
Balance as of July 31, 2020	$ 330,519,000
Number of operating segments \| operating_segment	2
Subsequent Event
Goodwill [Roll Forward]
Share price (in dollars per share) \| $ / shares		$ 13.32
Subsequent Event \| Common Stock
Goodwill [Roll Forward]
Share price (in dollars per share) \| $ / shares			$ 16.42
Solacom
Goodwill [Roll Forward]
Change related to acquisitions	$ (420,000)
GD NG-911
Goodwill [Roll Forward]
Change related to acquisitions	4,556,000
CGC
Goodwill [Roll Forward]
Change related to acquisitions	15,894,000
Balance as of July 31, 2020	15,894,000
Commercial Solutions
Goodwill [Roll Forward]
Balance as of July 31, 2019	251,296,000
Balance as of July 31, 2020	255,432,000
Commercial Solutions \| Subsequent Event
Goodwill [Roll Forward]
Percentage of fair value in excess of carrying amount for reporting unit			8.40%
Commercial Solutions \| Solacom
Goodwill [Roll Forward]
Change related to acquisitions	(420,000)
Commercial Solutions \| GD NG-911
Goodwill [Roll Forward]
Change related to acquisitions	4,556,000
Commercial Solutions \| CGC
Goodwill [Roll Forward]
Change related to acquisitions	0
Government Solutions
Goodwill [Roll Forward]
Balance as of July 31, 2019	59,193,000
Balance as of July 31, 2020	75,087,000
Government Solutions \| Subsequent Event
Goodwill [Roll Forward]
Percentage of fair value in excess of carrying amount for reporting unit			78.00%
Government Solutions \| Solacom
Goodwill [Roll Forward]
Change related to acquisitions	0
Government Solutions \| GD NG-911
Goodwill [Roll Forward]
Change related to acquisitions	0
Government Solutions \| CGC
Goodwill [Roll Forward]
Change related to acquisitions	$ 15,894,000