v2.4.1.9
Related Party Transactions - Consolidated Balance Sheet (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Receivables, net $ 6,321us-gaap_AccountsReceivableNetCurrent $ 6,376us-gaap_AccountsReceivableNetCurrent
Accounts payable and accrued expenses related to trade creditors 5,638us-gaap_AccountsPayableCurrent 5,528us-gaap_AccountsPayableCurrent
Accrued expenses and other current liabilities 5,293us-gaap_AccruedLiabilitiesCurrent 7,967us-gaap_AccruedLiabilitiesCurrent
Other noncurrent liabilities 10,819us-gaap_OtherLiabilitiesNoncurrent 11,384us-gaap_OtherLiabilitiesNoncurrent
NBCUniversal Media, LLC [Member]    
Receivables, net 4,842us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
4,911us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Accounts payable and accrued expenses related to trade creditors 1,388us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
1,583us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Accrued expenses and other current liabilities 1,422us-gaap_AccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
1,465us-gaap_AccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Note payable to Comcast 865cmcsa_NotesPayableToComcast
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
799cmcsa_NotesPayableToComcast
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Other noncurrent liabilities 3,722us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
3,412us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Transactions With Comcast And Consolidated Subsidiaries [Member] | NBCUniversal Media, LLC [Member]    
Receivables, net 229us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
228us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
Accounts payable and accrued expenses related to trade creditors 47us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
56us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
Accrued expenses and other current liabilities 8us-gaap_AccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
37us-gaap_AccruedLiabilitiesCurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
Note payable to Comcast 865cmcsa_NotesPayableToComcast
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
799cmcsa_NotesPayableToComcast
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
Other noncurrent liabilities $ 383us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember
$ 383us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= cmcsa_ComcastAndConsolidatedSubsidiariesMember