Programming and Production Costs (Narrative) (Details) $ in Billions	Dec. 31, 2021 USD ($)
Other Industries [Abstract]
Future minimum commitments for sports rights	$ 59.5
Future minimum commitments for licensed content	$ 5.5

Entertainment, License Agreement For Program Materials, Unrecorded Future Minimum Amount

No definition available.

Name:	cmcsa_EntertainmentLicenseAgreementForProgramMaterialsUnrecordedFutureMinimumAmount
Namespace Prefix:	cmcsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant