v2.4.0.8

Significant Transactions (Narrative) (Details) | Jun. 30, 2014
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Significant Transactions [Line Items] |
Percentage Of Voting Interests To Be Acquired | 100.00%
Company Shares Exchanged For Each Acquiree Share | 2.875
Acquiree Stockholders Percentage Ownership In Parent Company | 23.00%
Merger Agreement Undertaking Number Of Divested Customers [Member] |
Significant Transactions [Line Items] |
Number of customers | 3,000,000
Divestiture Transactions Net Disposition Of Customers [Member] |
Significant Transactions [Line Items] |
Number of customers | 3,900,000
Divestiture Transactions Customers To Be Spun Off In SpinCo [Member] |
Significant Transactions [Line Items] |
Number of customers | 2,500,000
Divestiture Transactions Like Kind Divestiture Of Time Warner Cable Customers [Member] |
Significant Transactions [Line Items] |
Number of customers | 1,500,000
Divestiture Transactions Like Kind Receipt Of Charter Communications Customers [Member] |
Significant Transactions [Line Items] |
Number of customers | 1,700,000
Divestiture Transactions Sale Of Time Warner Cable Customers Member [Member] |
Significant Transactions [Line Items] |
Number of customers | 1,500,000
Comcast Corporate Shareholders [Member] |
Significant Transactions [Line Items] |
Ownership Percentage In New Company | 67.00%
New Charter [Member] |
Significant Transactions [Line Items] |
Ownership Percentage In New Company | 33.00%

X
- Definition Represents the percentage ownership of the Company that will be held by Time Warner Cable stockholders estimated based on the number of shares outstanding as of the date of the agreement. + References No definition available. + Details
Name: | cmcsa_AcquireeStockholdersPercentageOwnershipInParentCompany
Namespace Prefix: | cmcsa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the amount of the Company's Class A common stock that Time Warner Cable stockholders will receive in exchange for each share of Time Warner Cable common stock owned immediately prior to the merger. + References No definition available. + Details
Name: | cmcsa_CompanySharesExchangedForEachAcquireeShare
Namespace Prefix: | cmcsa_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of customers + References No definition available. + Details
Name: | cmcsa_NumberOfCustomers
Namespace Prefix: | cmcsa_
Data Type: | xbrli:positiveIntegerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The ownership percentage in new company. + References No definition available. + Details
Name: | cmcsa_OwnershipPercentageInNewCompany
Namespace Prefix: | cmcsa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of voting equity interests to be acquired at the acquisition date in the business combination. + References No definition available. + Details
Name: | cmcsa_PercentageOfVotingInterestsToBeAcquired
Namespace Prefix: | cmcsa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | cmcsa_SignificantTransactionsLineItems
Namespace Prefix: | cmcsa_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration