v3.3.1.900

Commitments and Contingencies (Narrative) (Details) | Dec. 31, 2015 numberofemployees
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Number of employees covered under collective bargaining agreements | 7,500
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during the next fiscal year | 10.00%
NBCUniversal Media LLC [Member] |
Number of employees covered under collective bargaining agreements | 7,500
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during the next fiscal year | 10.00%

X
- Definition Number of NBCUniversal employees on our payroll covered by collective bargaining agreements. + References No definition available. + Details
Name: | cmcsa_NumberOfEmployeesCoveredUnderCollectiveBargainingAgreements
Namespace Prefix: | cmcsa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of NBCUniversal full-time equivalent employees that were covered by collective bargaining agreements that have expired or are scheduled to expire during the next year. + References No definition available. + Details
Name: | cmcsa_PercentageOfEmployeesCoveredUnderCollectiveBargainingAgreementsExpiredOrScheduledToExpireDuringNextYear
Namespace Prefix: | cmcsa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | cmcsa_LegalEntity1Axis=cmcsa_NBCUniversalMediaLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |