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Investments (Equity Method Investments) (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2018 | Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018 | Aug. 31, 2016 | Jul. 31, 2016
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Equity in net income (losses) of investees, net |  | $ 262 | $ (49) |  |  |
Equity method investments |  | 4,960 |  | $ 4,035 |  |
NBCUniversal Media LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Equity in net income (losses) of investees, net |  | (120) | (100) |  |  |
Equity method investments |  | 831 |  | 707 |  |
Atairos [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Equity in net income (losses) of investees, net |  | 374 | 35 |  |  |
Cash capital contributions for equity method investments |  | 37 | 31 |  |  |
Equity method investments |  | 3,100 |  | 2,700 |  |
Hulu [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Equity in net income (losses) of investees, net |  | (141) | (131) |  |  |
Cash capital contributions for equity method investments |  | 233 | 114 |  |  |
Equity method investments |  | 341 |  | 248 |  |
Ownership percentage |  |  |  |  | 30.00% | 33.00%
Hulu [Member] | NBCUniversal Media LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Equity in net income (losses) of investees, net |  | (141) | (131) |  |  |
Cash capital contributions for equity method investments |  | 233 | $ 114 |  |  |
Equity method investments |  | 341 |  | $ 248 |  |
Ownership percentage |  |  |  |  | 30.00% | 33.00%
Hulu [Member] | Equity Method Investments [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Recognition of previously deferred gain |  | 159 |  |  |  |
Hulu [Member] | Equity Method Investments [Member] | NBCUniversal Media LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Recognition of previously deferred gain |  | $ 159 |  |  |  |
Hulu [Member] | Time Warner, Inc. [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership percentage |  |  |  |  | 10.00% |
Hulu [Member] | Time Warner, Inc. [Member] | NBCUniversal Media LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership percentage |  |  |  |  | 10.00% |
The Weather Channel [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Pretax gain on sale of investment | $ 64 |  |  |  |  |
The Weather Channel [Member] | NBCUniversal Media LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Pretax gain on sale of investment | $ 64 |  |  |  |  |

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