v2.4.1.9

Condensed Consolidating Financial Information (Narrative) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014
Comcast Holdings' ZONES due October 2029 [Member] |
Debt Instrument, Maturity Date, Description | October 2029
Principal amount of debt securities subject to guarantee | $ 185,000,000 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_ComcastHoldingsZonesDueOctober2029Member
Comcast Holdings' ZONES due November 2029 [Member] |
Debt Instrument, Maturity Date, Description | November 2029
Principal amount of debt securities not subject to guarantee | 62,000,000 cmcsa_NonGuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_ComcastHoldingsZonesDueNovember2029Member
Guarantor Subsidiaries [Member] |
Principal amount of debt securities subject to guarantee | 32,600,000,000 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = us-gaap_GuarantorSubsidiariesMember
Maturing In Next Five Years [Member] |
Principal amount of debt securities subject to guarantee | 9,300,000,000 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_MaturingInNextFiveYearsMember
NBCUniversal Enterprise Credit Facility [Member] |
Debt Instrument, Maturity Date, Description | March 2018
Credit facility borrowing capacity | 1,350,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DerivativeByNatureAxis = us-gaap_RevolvingCreditFacilityMember
Comcast And Comcast Cable Communications LLC [Member] |
Debt Instrument, Maturity Date, Description | June 2017
Credit facility borrowing capacity | 6,250,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity / us-gaap_DerivativeByNatureAxis = cmcsa_ComcastAndComcastCableCommunicationsLlcMember
NBCUniversal Enterprise [Member] |
Principal amount of debt securities subject to guarantee | $ 4,000,000,000 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_NbcuniversalEnterpriseMember

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