v2.4.0.8

Commitments and Contingencies (Narrative) (Details) | Dec. 31, 2013 numberofemployees
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Number of employees covered under collective bargaining agreements | 7,200
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during 2014 | 19.00%
NBCUniversal Media, LLC [Member] |
Number of employees covered under collective bargaining agreements | 7,200
Percentage of employees covered under collective bargaining agreements that have expired or are scheduled to expire during 2014 | 19.00%

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