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Condensed Consolidating Financial Information (Narrative) (Details) $ in Millions | Jun. 30, 2018 USD ($)
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NBCUniversal Enterprise Senior Debt Securities [Member] |
Debt Instrument [Line Items] |
Principal amount of debt securities subject to guarantee | $ 3,000
NBCUniversal Enterprise Credit Facility [Member] |
Debt Instrument [Line Items] |
Revolving credit facility subject to guarantee | 1,500
Universal Studios Japan Term Loan Maturing March 2022 [Member] |
Debt Instrument [Line Items] |
Term loans subject to guarantee | 3,600
Comcast Holdings' ZONES due October 2029 [Member] |
Debt Instrument [Line Items] |
Principal amount of debt securities subject to guarantee | 185
Comcast Holdings' ZONES due November 2029 [Member] |
Debt Instrument [Line Items] |
Principal amount of debt securities not subject to guarantee | $ 62

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