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Income Taxes (Components of Net Deferred Tax Liability) (Details) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2014
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Dec. 31, 2013
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|---|---|---|
| Net operating loss carryforwards | $ 448us-gaap_DeferredTaxAssetsOperatingLossCarryforwards | $ 495us-gaap_DeferredTaxAssetsOperatingLossCarryforwards |
| Differences between book and tax basis of long-term debt | 116us-gaap_DeferredTaxAssetsOther | 117us-gaap_DeferredTaxAssetsOther |
| Nondeductible accruals and other | 3,383us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther | 3,588us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther |
| Less: Valuation allowance | 375us-gaap_DeferredTaxAssetsValuationAllowance | 405us-gaap_DeferredTaxAssetsValuationAllowance |
| Total deferred tax assets | 3,572us-gaap_DeferredTaxAssetsNet | 3,795us-gaap_DeferredTaxAssetsNet |
| Total deferred tax liabilities | 36,336us-gaap_DeferredIncomeTaxLiabilities | 35,494us-gaap_DeferredIncomeTaxLiabilities |
| Net deferred tax liability | 32,764us-gaap_DeferredTaxLiabilities | 31,699us-gaap_DeferredTaxLiabilities |
| Property And Equipment And Intangible Assets [Member] | ||
| Deferred tax liabilities, other | 35,112us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_PropertyAndEquipmentAndIntangibleAssetsMember |
34,044us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_PropertyAndEquipmentAndIntangibleAssetsMember |
| Investments [Member] | ||
| Deferred tax liabilities, other | 186us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = us-gaap_InvestmentsMember |
473us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = us-gaap_InvestmentsMember |
| Indexed Debt Securities [Member] | ||
| Deferred tax liabilities, other | 534us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_IndexedDebtSecuritiesMember |
610us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_IndexedDebtSecuritiesMember |
| Foreign Subsidiaries And Undistributed Foreign Earnings [Member] | ||
| Deferred tax liabilities, other | $ 504us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_ForeignSubsidiariesAndUndistributedForeignEarningsMember |
$ 367us-gaap_DeferredTaxLiabilitiesOther / cmcsa_TaxAdjustmentsAxis = cmcsa_ForeignSubsidiariesAndUndistributedForeignEarningsMember |
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- Definition
Amount of deferred tax liability attributable to taxable temporary differences. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from other reserves and accruals not separately disclosed. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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