v2.4.0.6

Investments (Cost Method Investments) (Details) (Air Touch [Member], USD $) In Billions, unless otherwise specified | Jun. 30, 2012
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Air Touch [Member] |
Fair value amount of redeemable preferred stock | $ 1.9

X
- Definition Fair value of our redeemable subsidiary preferred stock. + References No definition available. + Details
Name: | cmcsa_FairValueAmountOfRedeemablePreferredStock
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant