Long-Term Debt (Narrative) (Details) $ in Millions	6 Months Ended
Jun. 30, 2016 USD ($)
Total debt	$ 55,600
Long-term Debt, Fair Value	64,400
Amounts available under revolving credit facilities	7,100
NBCUniversal Media LLC [Member]
Total debt	12,000
Long-term Debt, Fair Value	$ 13,500
Comcast ownership in cable holding company subsidiaries	100.00%
NBCUniversal Enterprise [Member]
Commercial paper	$ 1,200
NBCUniversal Enterprise [Member] \| NBCUniversal Media LLC [Member]
Related Party Aggregate Principal Amount Senior Notes Not Subject To Guarantee	3,300
Related Party Credit Facility Not Subject To Guarantee	1,500
Related Party Liquidation Preference Preferred Stock Not Subject To Guarantee	725
Comcast Revolving Credit Facility [Member]
Credit facility borrowing capacity	$ 7,000
Maturity date	2021
Potential Increased Credit Facility Borrowing Capacity	$ 10,000
Potential Extended Credit Facility Maturity Date	2023
Borrowing margin for LIBOR based borrowings	1.00%
Comcast Revolving Credit Facility [Member] \| NBCUniversal Media LLC [Member]
Maturity date	2021
Revolver Line of credit amount outstanding	$ 0
Guarantee Obligations Current Principal Balance	7,000
NBCUniversal Enterprise Credit Facility [Member]
Credit facility borrowing capacity	$ 1,500
Maturity date	2021
Potential Increased Credit Facility Borrowing Capacity	$ 2,000
Potential Extended Credit Facility Maturity Date	2023
Borrowing margin for LIBOR based borrowings	1.00%
Amounts available under revolving credit facilities	$ 326
Former Comcast and Comcast Cable Communications, LLC Revolving Credit Facility Member [Member]
Credit facility borrowing capacity	6,250
Former NBCUniversal Enterprise Credit Facility [Member]
Credit facility borrowing capacity	1,350
Comcast And Comcast Cable Debt Securities [Member] \| NBCUniversal Media LLC [Member]
Guarantee Obligations Current Principal Balance	$ 38,500

Represents the Company's ownership in its cable holding company subsidiaries.

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Description of the potential extended credit facility maturity date, subject to approval of the lenders.

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Principal amount of debt securities subject to guarantee.

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Potential increased maximum borrowing capacity under the revolving credit facility, subject to approval of the lenders.

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Represents the related party aggregate principal amount of senior notes not subject to guarantee by NBCUniversal.

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Represents the related party credit facility not subject to guarantee by NBCUniversal.

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Represents the related party liquidation preference of preferred stock not subject to guarantee by NBCUniversal.

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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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