The aggregate principal amount of the debt being exchanged in a debt exchange transaction.

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Note Receivable From Ultimate Parent, Noncurrent

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Percentage points added to the reference rate to compute the variable rate on dividend payments on preferred stock; the variable rate will reset every 5 years

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Repayment to ultimate parent including cash management arrangement under the matching revolving credit facilities.

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The maximum amount of borrowing or lending capacity including the cash management arrangement between ultimate parent and subsidiary under the matching revolving credit facilities.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer.

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The percentage rate used to calculate dividend payments on preferred stock.

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Value of the difference between preference in liquidation and the par or stated values of the preferred shares.

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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.

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Amount of cash outflow for the payment of debt classified as other.

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Related Party Transactions (Narrative) (Details) - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 01, 2018	Oct. 31, 2017	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Repayments of Debt				$ 14,354,000,000	$ 8,798,000,000	$ 6,364,000,000
Other noncurrent liabilities				16,765,000,000	15,329,000,000
Recognized share-based compensation expense				825,000,000	639,000,000	586,000,000
Restricted share units [Member]
Related Party Transaction [Line Items]
Recognized share-based compensation expense				564,000,000	402,000,000	349,000,000
Unrecognized pretax compensation expense on nonvested awards				$ 1,100,000,000
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)				1 year 6 months
Stock options [Member]
Related Party Transaction [Line Items]
Recognized share-based compensation expense				$ 231,000,000	205,000,000	205,000,000
Unrecognized pretax compensation expense on nonvested awards				$ 493,000,000
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)				1 year 8 months 12 days
NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Note receivable from Comcast				$ 1,069,000,000	0
Repayments of Debt				3,778,000,000	438,000,000	3,498,000,000
Other noncurrent liabilities				6,548,000,000	5,177,000,000
Recognized share-based compensation expense				188,000,000	151,000,000	133,000,000
NBCUniversal Media LLC [Member] \| Restricted share units [Member]
Related Party Transaction [Line Items]
Unrecognized pretax compensation expense on nonvested awards				$ 308,000,000
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)				1 year 6 months
NBCUniversal Media LLC [Member] \| Stock options [Member]
Related Party Transaction [Line Items]
Unrecognized pretax compensation expense on nonvested awards				$ 13,000,000
Unrecognized pretax compensation expense on nonvested awards, weighted average period of recognition (in years)				8 months 12 days
NBCUniversal Media LLC [Member] \| Carrying Value Of Related Party Contractual Obligation [Member]
Related Party Transaction [Line Items]
Other noncurrent liabilities				$ 383,000,000	383,000,000
NBCUniversal Media LLC [Member] \| NBCUniversal Holdings Preferred Stock [Member]
Related Party Transaction [Line Items]
Preferred stock, dividend rate				8.25%
Preferred stock liquidation preference value				$ 9,400,000,000
Preferred stock dividend rate, spread on variable rate	7.44%
NBCUniversal Media LLC [Member] \| Comcast and NBCUniversal Revolving Credit Agreements [Member]
Related Party Transaction [Line Items]
Revolving credit agreement capacity							$ 5,000,000,000
NBCUniversal Media LLC [Member] \| Comcast and Consolidated Subsidiaries [Member]
Related Party Transaction [Line Items]
Note receivable from Comcast				1,069,000,000	0
Other noncurrent liabilities				454,000,000	$ 410,000,000
Notes Payable [Member] \| 4.00% Notes Due 2049 [Member] \| NBCUniversal Media LLC [Member] \| Comcast and Consolidated Subsidiaries [Member]
Related Party Transaction [Line Items]
Repayments of Debt				$ 610,000,000
Interest rate				4.00%
Gain (loss) on extinguishment of debt			$ 178,000,000
Senior Notes Exchange [Member] \| Senior Notes [Member] \| Comcast and NBCUniversal Senior Notes [Member]
Related Party Transaction [Line Items]
Aggregate principal amount						5,500,000,000
Amount of debt exchanged						$ 3,900,000,000
Senior Notes Exchange [Member] \| Senior Notes [Member] \| Comcast and NBCUniversal Senior Notes [Member] \| NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Amount of debt exchanged		$ 3,900,000,000
Senior Notes Exchange [Member] \| Senior Notes [Member] \| Senior 6.40% Notes Due 2040 [Member] \| NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Interest rate		6.40%
Amount of debt exchanged		$ 442,000,000
Senior Notes Exchange [Member] \| Senior Notes [Member] \| Senior 6.40% Notes Due 2040 [Member] \| NBCUniversal Media LLC [Member] \| Comcast and Consolidated Subsidiaries [Member]
Related Party Transaction [Line Items]
Gain (loss) on extinguishment of debt		157,000,000
Senior Notes Exchange [Member] \| Notes Payable [Member] \| 4.00% Notes Due 2049 [Member] \| NBCUniversal Media LLC [Member] \| Comcast and Consolidated Subsidiaries [Member]
Related Party Transaction [Line Items]
Aggregate principal amount		$ 610,000,000
Interest rate		4.00%
Non-Interest Bearing Notes Due 2024 [Member] \| NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Note receivable from Comcast				$ 1,300,000,000
Comcast And NBCUniveral Revolving Credit Agreements [Member] \| NBCUniversal Media LLC [Member]
Related Party Transaction [Line Items]
Repayments of debt				$ 1,000,000,000.0