Recent Accounting Pronouncements (Effect of Changes in Revenue Recognition - Cable Communications Segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 27,846	$ 22,135	$ 21,735	$ 22,791	$ 22,075	$ 21,081	$ 21,286	$ 20,587	$ 94,507	$ 85,029	$ 80,736
Depreciation and Amortization									11,017	10,130	9,426
Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									55,143	53,070	50,577
Operating costs and expenses										32,002	30,563
Depreciation and Amortization										8,006	7,538
Residential, Video [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									22,455	22,874	22,204
Residential, High-Speed Internet [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									17,144	15,681	14,421
Residential, Voice [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									3,960	4,090	4,159
Business Services [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									7,129	6,437	5,705
Advertising [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									2,795	2,450	2,626
Other [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue									$ 1,660	1,538	1,462
Previous Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										84,526	80,403
Previous Reported [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										52,519	50,048
Operating costs and expenses										31,349	29,939
Depreciation and Amortization										8,143	7,670
Previous Reported [Member] | Residential, Video [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										23,129	22,357
Previous Reported [Member] | Residential, High-Speed Internet [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										14,769	13,532
Previous Reported [Member] | Residential, Voice [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										3,391	3,540
Previous Reported [Member] | Business Services [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										6,216	5,514
Previous Reported [Member] | Advertising [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										2,257	2,476
Previous Reported [Member] | Other [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										2,757	2,629
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										503	333
Effects of Adoption [Member] | Accounting Standards Update 2014-09 [Member] | Cable Communications [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue										551	529
Operating costs and expenses										653	624
Depreciation and Amortization										(137)	(132)
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										(255)	(153)
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										912	889
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										699	619
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										221	191
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										193	150
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										$ (1,219)	$ (1,167)