v2.4.0.6

Receivables Monetization (Narrative)(Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2012 | Dec. 31, 2011
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Receivables Monetization [Abstract] |  |
Securitization programs payable | $ 712 | $ 781

X
- Definition This element represents cash receipts that have not yet been remitted to the monetization program as of the balance sheet date and are recorded within accounts payable and accrued expenses related to trade creditors. + References No definition available. + Details
Name: | cmcsa_MonetizationCollectionsOwedUnderProgram
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration