Amount of film and television costs acquired at the acquisition date.

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Amount of liability for a tax receivable agreement acquired at the acquisition date.

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The amount of acquisition cost of a business combination allocated to other noncurrent assets and liabilities of the acquired entity not otherwise disclosed separately.

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The amount of working capital (current assets less current liabilities, including cash if any) acquired as of the acquisition date.

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Contribution from member including, but not limited to, a business, investment or asset.

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This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of deferred tax asset attributable to deductible temporary differences and carryforwards acquired at the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Significant Transactions (Allocation of Purchase Price) (Details) - USD ($) $ in Millions		12 Months Ended
	Aug. 22, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill (see Note 9)		$ 36,780	$ 35,980	$ 32,945
NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill (see Note 9)		23,989	23,323	20,364
Contribution from member		$ 662	$ 3,655	$ 252
DreamWorks Animation [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Film and television costs	$ 838
Intangible assets	396
Working capital	156
Debt	(381)
Tax receivable agreement	(146)
Deferred income taxes	291
Other noncurrent assets (liabilities)	170
Identifiable net assets (liabilities) acquired	1,324
Noncontrolling interests	(337)
Goodwill (see Note 9)	2,786
Cash consideration transferred by Comcast	3,773
DreamWorks Animation [Member] \| NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Film and television costs	838
Intangible assets	396
Working capital	156
Debt	(381)
Tax receivable agreement	(146)
Other noncurrent assets (liabilities)	461
Identifiable net assets (liabilities) acquired	1,324
Noncontrolling interests	(337)
Goodwill (see Note 9)	2,786
Cash consideration transferred by Comcast	3,773
DreamWorks Animation [Member] \| Member's contribution that represented Deferred Income Tax Assets and Other Tax-related Items recorded by Parent but excluded from net assets contributed [Member] \| NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contribution from member	279
DreamWorks Animation [Member] \| Tax Receivable Agreement [Member] \| NBCUniversal Media LLC [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Contribution from member	$ 146