v2.4.1.9

Condensed Consolidating Financial Information (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Comcast Holdings' ZONES due October 2029 [Member] |
Debt Instrument, Maturity Date, Description | October 2029
Principal amount of debt securities subject to guarantee | $ 185 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 cmcsa_NonGuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_ComcastHoldingsZonesDueNovember2029Member
NBCUniversal Enterprise Credit Facility [Member] |
Debt Instrument, Maturity Date, Description | March 2018
Principal amount of debt securities subject to guarantee | 1,350 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = us-gaap_RevolvingCreditFacilityMember
Comcast And Comcast Cable Communications LLC [Member] |
Debt Instrument, Maturity Date, Description | June 2017
Principal amount of debt securities subject to guarantee | 6,250 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_ComcastAndComcastCableCommunicationsLlcMember
NBCUniversal Enterprise [Member] |
Principal amount of debt securities subject to guarantee | $ 4,000 cmcsa_GuaranteeObligationsCurrentPrincipalBalance / us-gaap_DerivativeByNatureAxis = cmcsa_NbcuniversalEnterpriseMember

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