v3.5.0.2

Fair Value Disclosure (Narrative) (Details) $ in Millions | Jun. 30, 2016 USD ($)
--- | ---
NBCUniversal Enterprise [Member] |
Fair value of redeemable preferred stock | $ 761

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

X
- Details
Name: | dei_LegalEntityAxis=cmcsa_NbcuniversalEnterpriseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |