XML 55 R41.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Long-Term Debt (Debt Borrowings)(Details) - USD ($) $ in Millions | 6 Months Ended
--- | ---
Jun. 30, 2018 | Jun. 30, 2017
Debt Instrument [Line Items] |  |
Proceeds from borrowings | $ 4,279 | $ 8,963
Universal Beijing Resort term loans [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | 235 |
Other [Member] |  |
Debt Instrument [Line Items] |  |
Other | 44 |
Senior Notes [Member] | Senior 3.90% notes due 2038 [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | $ 1,200 |
Interest rate | 3.90% |
Senior Notes [Member] | Senior 3.55% notes due 2028 [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | $ 1,000 |
Interest rate | 3.55% |
Senior Notes [Member] | Senior 4.00% notes due 2048 [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | $ 1,000 |
Interest rate | 4.00% |
Senior Notes [Member] | Senior 4.25% notes due 2053 [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | $ 800 |
Interest rate | 4.25% |
Secured Debt [Member] | Universal Beijing Resort term loans [Member] |  |
Debt Instrument [Line Items] |  |
Debt face amount | $ 235 |

X
- Definition Amount of debt discount (premium) and other borrowings. + References No definition available. + Details
Name: | cmcsa_DebtInstrumentUnamortizedDiscountPremiumNetandOtherBorrowings
Namespace Prefix: | cmcsa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_UniversalBeijingResortTermLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_OtherBorrowingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_Senior3.90NotesDue2038Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_Senior3.55NotesDue2028Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_Senior4.00NotesDue2048Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cmcsa_Senior4.25NotesDue2053Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |