v2.4.1.9
Supplemental Financial Information (Net Cash Provided by Operating Activities)(Details) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Net income $ 2,141,000,000us-gaap_ProfitLoss $ 1,938,000,000us-gaap_ProfitLoss
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation and amortization 2,066,000,000us-gaap_DepreciationAndAmortization 1,970,000,000us-gaap_DepreciationAndAmortization
Share-based compensation 135,000,000us-gaap_ShareBasedCompensation 119,000,000us-gaap_ShareBasedCompensation
Noncash interest expense (income), net 51,000,000cmcsa_NoncashInterestExpenseIncomeNet 42,000,000cmcsa_NoncashInterestExpenseIncomeNet
Equity in net (income) losses of investees, net (33,000,000)us-gaap_IncomeLossFromEquityMethodInvestments (32,000,000)us-gaap_IncomeLossFromEquityMethodInvestments
Cash received from investees 22,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions 18,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
Net (gain) loss on investment activity and other (121,000,000)cmcsa_GainLossOnInvestmentsAndNoncashOtherIncomeExpenseNet (59,000,000)cmcsa_GainLossOnInvestmentsAndNoncashOtherIncomeExpenseNet
Deferred income taxes (119,000,000)us-gaap_DeferredIncomeTaxExpenseBenefit (226,000,000)us-gaap_DeferredIncomeTaxExpenseBenefit
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:    
Current and noncurrent receivables, net 119,000,000cmcsa_ChangeInCurrentAndNoncurrentReceivablesNet 195,000,000cmcsa_ChangeInCurrentAndNoncurrentReceivablesNet
Film and television costs, net (38,000,000)cmcsa_FilmAndTelevisionCostsNet 154,000,000cmcsa_FilmAndTelevisionCostsNet
Accounts payable and accrued expenses related to trade creditors (cash flow) 372,000,000us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities 82,000,000us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities
Other operating assets and liabilities 650,000,000us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet 285,000,000us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet
Net cash provided by operating activities 5,245,000,000us-gaap_NetCashProvidedByUsedInOperatingActivities 4,486,000,000us-gaap_NetCashProvidedByUsedInOperatingActivities
NBCUniversal Media, LLC [Member]    
Net income 918,000,000us-gaap_ProfitLoss
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
741,000,000us-gaap_ProfitLoss
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation and amortization 364,000,000us-gaap_DepreciationAndAmortization
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
365,000,000us-gaap_DepreciationAndAmortization
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Equity in net (income) losses of investees, net (20,000,000)us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
(18,000,000)us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Cash received from investees 12,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
12,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Net (gain) loss on investment activity and other 46,000,000cmcsa_GainLossOnInvestmentsAndNoncashOtherIncomeExpenseNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
21,000,000cmcsa_GainLossOnInvestmentsAndNoncashOtherIncomeExpenseNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Deferred income taxes 3,000,000us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
16,000,000us-gaap_DeferredIncomeTaxExpenseBenefit
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:    
Current and noncurrent receivables, net (106,000,000)cmcsa_ChangeInCurrentAndNoncurrentReceivablesNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
55,000,000cmcsa_ChangeInCurrentAndNoncurrentReceivablesNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Film and television costs, net (36,000,000)cmcsa_FilmAndTelevisionCostsNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
148,000,000cmcsa_FilmAndTelevisionCostsNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Accounts payable and accrued expenses related to trade creditors (cash flow) 16,000,000us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
(117,000,000)us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Other operating assets and liabilities 5,000,000us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
(467,000,000)us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
Net cash provided by operating activities $ 1,202,000,000us-gaap_NetCashProvidedByUsedInOperatingActivities
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember
$ 756,000,000us-gaap_NetCashProvidedByUsedInOperatingActivities
/ dei_LegalEntityAxis
= cmcsa_NBCUniversalMediaLLCMember