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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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