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Supplemental Financial Information (Receivables)(Details) (USD $)
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Dec. 31, 2014
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Dec. 31, 2013
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|---|---|---|
| Receivables, gross | $ 6,885,000,000us-gaap_AccountsReceivableGrossCurrent | $ 6,972,000,000us-gaap_AccountsReceivableGrossCurrent |
| Less: Allowance for returns and customer incentives | 359,000,000cmcsa_ReturnsAndIncentivesAllowance | 375,000,000cmcsa_ReturnsAndIncentivesAllowance |
| Less: Allowance for doubtful accounts | 205,000,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent | 221,000,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent |
| Receivables, net | 6,321,000,000us-gaap_AccountsReceivableNetCurrent | 6,376,000,000us-gaap_AccountsReceivableNetCurrent |
| Noncurrent receivables, net | 569,000,000us-gaap_AccountsReceivableNetNoncurrent | 488,000,000us-gaap_AccountsReceivableNetNoncurrent |
| NBCUniversal Media, LLC [Member] | ||
| Receivables, gross | 5,258,000,000us-gaap_AccountsReceivableGrossCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
5,348,000,000us-gaap_AccountsReceivableGrossCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
| Less: Allowance for returns and customer incentives | 356,000,000cmcsa_ReturnsAndIncentivesAllowance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
372,000,000cmcsa_ReturnsAndIncentivesAllowance / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
| Less: Allowance for doubtful accounts | 60,000,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
65,000,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
| Receivables, net | 4,842,000,000us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
4,911,000,000us-gaap_AccountsReceivableNetCurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
| Noncurrent receivables, net | $ 569,000,000us-gaap_AccountsReceivableNetNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
$ 488,000,000us-gaap_AccountsReceivableNetNoncurrent / dei_LegalEntityAxis = cmcsa_NBCUniversalMediaLLCMember |
| X | ||||||||||
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- Definition
A valuation allowance for sales returns and other incentives. No definition available.
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| X | ||||||||||
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- Definition
Amounts due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer) for goods or services (including trade receivables) that have been delivered or sold in the normal course of business. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Amount due from customers or clients, more than one year from the balance sheet date, for goods or services that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Details
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