v2.4.1.9

Related Party Transactions - Consolidated Balance Sheet (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Receivables, net | $ 6,321 us-gaap_AccountsReceivableNetCurrent | $ 6,376 us-gaap_AccountsReceivableNetCurrent
Accounts payable and accrued expenses related to trade creditors | 5,638 us-gaap_AccountsPayableCurrent | 5,528 us-gaap_AccountsPayableCurrent
Accrued expenses and other current liabilities | 5,293 us-gaap_AccruedLiabilitiesCurrent | 7,967 us-gaap_AccruedLiabilitiesCurrent
Other noncurrent liabilities | 10,819 us-gaap_OtherLiabilitiesNoncurrent | 11,384 us-gaap_OtherLiabilitiesNoncurrent
NBCUniversal Media, LLC [Member] |  |
Receivables, net | 4,842 us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember | 4,911 us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember
Accounts payable and accrued expenses related to trade creditors | 1,388 us-gaap_AccountsPayableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember | 1,583 us-gaap_AccountsPayableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember
Accrued expenses and other current liabilities | 1,422 us-gaap_AccruedLiabilitiesCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember | 1,465 us-gaap_AccruedLiabilitiesCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember
Note payable to Comcast | 865 cmcsa_NotesPayableToComcast / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember | 799 cmcsa_NotesPayableToComcast / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember
Other noncurrent liabilities | 3,722 us-gaap_OtherLiabilitiesNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember | 3,412 us-gaap_OtherLiabilitiesNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember
Transactions With Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media, LLC [Member] |  |
Receivables, net | 229 us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember | 228 us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember
Accounts payable and accrued expenses related to trade creditors | 47 us-gaap_AccountsPayableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember | 56 us-gaap_AccountsPayableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember
Accrued expenses and other current liabilities | 8 us-gaap_AccruedLiabilitiesCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember | 37 us-gaap_AccruedLiabilitiesCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember
Note payable to Comcast | 865 cmcsa_NotesPayableToComcast / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember | 799 cmcsa_NotesPayableToComcast / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember
Other noncurrent liabilities | $ 383 us-gaap_OtherLiabilitiesNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember | $ 383 us-gaap_OtherLiabilitiesNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cmcsa_ComcastAndConsolidatedSubsidiariesMember

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