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Recent Accounting Pronouncements and Tax Reform (Effect of Changes in Revenue Recognition - Cable Communications Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 21,735	$ 21,286	$ 44,526	$ 41,873
Depreciation and Amortization	2,603	2,507	5,202	4,975
Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	13,710	13,257	27,228	26,307
Operating costs and expenses		7,964		15,840
Depreciation and Amortization		1,967		3,913
Residential, Video [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	5,628	5,740	11,287	11,446
Residential, High-Speed Internet [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	4,262	3,898	8,419	7,740
Residential, Voice [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	994	1,034	2,000	2,068
Business Services [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	1,761	1,585	3,487	3,128
Advertising [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	666	626	1,248	1,180
Other [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 399	374	$ 787	745
Previous Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		21,165		41,628
Previous Reported [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		13,122		26,034
Operating costs and expenses		7,802		15,516
Depreciation and Amortization		2,001		3,981
Previous Reported [Member] | Residential, Video [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		5,797		11,571
Previous Reported [Member] | Residential, High-Speed Internet [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		3,679		7,285
Previous Reported [Member] | Residential, Voice [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		856		1,719
Previous Reported [Member] | Business Services [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		1,531		3,021
Previous Reported [Member] | Advertising [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		574		1,086
Previous Reported [Member] | Other [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		685		1,352
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		121		245
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		135		273
Operating costs and expenses		162		324
Depreciation and Amortization		(34)		(68)
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Residential, Video [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		(57)		(125)
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Residential, High-Speed Internet [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		219		455
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Residential, Voice [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		178		349
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Business Services [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		54		107
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Advertising [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		52		94
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Other [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		$ (311)		$ (607)

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