v2.4.1.9

Commitments and Contingencies (Minimum Annual Commitments under the Programming License Agreements and Operating Leases) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014
Programming and talent commitments future minimum payments, 2015 | $ 4,915 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsCurrent
Programming and talent commitments future minimum payments, 2016 | 4,657 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInTwoYears
Programming and talent commitments future minimum payments, 2017 | 3,177 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInThreeYears
Programming and talent commitments future minimum payments, 2018 | 3,999 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFourYears
Programming and talent commitments future minimum payments, 2019 | 2,793 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFiveYears
Programming and talent commitments future minimum payments, thereafter | 26,130 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsDueThereafter
Operating leases future minimum payments, 2015 | 399 us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent
Operating leases future minimum payments, 2016 | 359 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears
Operating leases future minimum payments, 2017 | 299 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears
Operating leases future minimum payments, 2018 | 253 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears
Operating leases future minimum payments, 2019 | 197 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears
Operating leases future minimum payments, thereafter | 754 us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter
NBCUniversal Media, LLC [Member] |
Programming and talent commitments future minimum payments, 2015 | 4,898 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsCurrent / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Programming and talent commitments future minimum payments, 2016 | 4,648 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInTwoYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Programming and talent commitments future minimum payments, 2017 | 3,173 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInThreeYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Programming and talent commitments future minimum payments, 2018 | 3,998 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFourYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Programming and talent commitments future minimum payments, 2019 | 2,793 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFiveYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Programming and talent commitments future minimum payments, thereafter | 26,130 cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsDueThereafter / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, 2015 | 150 us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, 2016 | 135 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, 2017 | 107 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, 2018 | 89 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, 2019 | 73 us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember
Operating leases future minimum payments, thereafter | $ 402 us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter / cmcsa_LegalEntity1Axis = cmcsa_NBCUniversalMediaLLCMember

X
- Definition Programming And Talent Commitments Future Minimum Payments Current + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsCurrent
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Programming and talent commitments future minimum payments due thereafter + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsDueThereafter
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Programming And Talent Commitments Future Minimum Payments In Five Years + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFiveYears
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Programming and talent commitments future minimum payments in four years + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInFourYears
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Programming and talent commitments future minimum payments in three years + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInThreeYears
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Programming and talent commitments future minimum payments in two years + References No definition available. + Details
Name: | cmcsa_ProgrammingAndTalentCommitmentsFutureMinimumPaymentsInTwoYears
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of required minimum rental payments maturing in the next fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of required minimum rental payments maturing in the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of required minimum rental payments maturing in the forth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of required minimum rental payments maturing in the third fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of required minimum rental payments maturing in the second fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of required minimum rental payments maturing after the fifth fiscal year following the latest fiscal year for operating leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717 + Details
Name: | us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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