Name:	cmcsa_EntertainmentLicenseAgreementForProgramMaterialIncludingSportsRightsAdvancesAmortizationExpense
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Film And Television Content

No definition available.

Name:	cmcsa_FilmAndTelevisionContentAbstract
Namespace Prefix:	cmcsa_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of amortization expense for capitalized film cost for film predominantly monetized on its own and participation and residuals expenses.

No definition available.

Name:	cmcsa_FilmMonetizedOnItsOwnAmortizationExpenseIncludingParticipationsAndResiduals
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Other Programming And Production Expense

No definition available.

Name:	cmcsa_OtherProgrammingAndProductionExpense
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of expense recognized in the period for costs associated with video programming and content acquisition and production costs. Programming expenses include the fees paid to license the programming distributed to video customers, such as the programming license fees charged by cable networks and fees charged for retransmission of the signals from local broadcast television stations. Production costs include the amortization of owned and acquired programming, sports rights, direct production costs, residual and participation payments, production overhead, costs associated with the distribution of programming to third-party networks and other distribution platforms, and on-air talent costs. It also includes the amortization of capitalized theatrical film production and acquisition costs and distribution expenses.

No definition available.

Name:	cmcsa_ProgrammingAndProductionCosts
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Video Distribution Programming Expense

No definition available.

Name:	cmcsa_VideoDistributionProgrammingExpense
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of amortization expense for capitalized film cost for film predominantly monetized on its own.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 926
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483154/926-20-50-4A

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

Indicates line item in statement of income or comprehensive income that includes amortization expense for film cost of film predominantly monetized on its own.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 926
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483154/926-20-50-4A

Name:	us-gaap_FilmMonetizedOnItsOwnAmortizationExpenseStatementOfIncomeExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.