v2.4.0.8

Pension Plans and Postretirement Benefits (Deferred Compensation Plans) (Details) (USD $) In Millions, unless otherwise specified | 11 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2011 NBCUniversal Media, LLC [Member] | Dec. 31, 2013 NBCUniversal Media, LLC [Member] | Dec. 31, 2012 NBCUniversal Media, LLC [Member] | Dec. 31, 2013 Deferred Compensation Plans [Member] | Dec. 31, 2012 Deferred Compensation Plans [Member] | Dec. 31, 2011 Deferred Compensation Plans [Member]
Benefit obligation | $ 114 | $ 250 | $ 163 | $ 1,434 | $ 1,247 | $ 1,059
Interest expense | $ 10 | $ 18 | $ 11 | $ 128 | $ 107 | $ 99

X
- Definition Deferred compensation plans benefit obligation + References No definition available. + Details
Name: | cmcsa_DeferredCompensationPlansBenefitObligation
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Deferred compensation plans interest cost + References No definition available. + Details
Name: | cmcsa_DeferredCompensationPlansInterestCost
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration