Name:	cmcm_LoansGrantedToNomineeShareholdersAndViesByPrimaryBeneficiaries
Namespace Prefix:	cmcm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Maximum percentage of foreign ownership of PRC companies.

No definition available.

Name:	cmcm_MaximumPercentageOfForeignOwnershipOfPRCCompanies
Namespace Prefix:	cmcm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Represents the notice period for termination of agreement to be provided with in expiration.

No definition available.

Name:	cmcm_PeriodOfNoticeForTerminationBeforeExpiration
Namespace Prefix:	cmcm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the term of business operation agreement.

No definition available.

Name:	cmcm_TermOfBusinessOperationAgreement
Namespace Prefix:	cmcm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 25
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481231/810-10-45-25

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (bb)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 25
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481231/810-10-45-25

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

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

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481203/810-10-50-5A

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Name:	srt_ConsolidatedEntitiesAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_TypeOfArrangementAxis=cmcm_ShareholderVotingProxyAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_TypeOfArrangementAxis=cmcm_BusinessOperationAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ConsolidatedEntitiesAxis=cmcm_BeijingCheetahMobileTechnologyCo.Ltd.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_TitleOfIndividualAxis=cmcm_MrShengFuMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_TitleOfIndividualAxis=cmcm_MsWeiqinQiuMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ConsolidatedEntitiesAxis=cmcm_BeijingCheetahNetworkTechnologyCoLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_TitleOfIndividualAxis=cmcm_MrKunWangMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: