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Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Related Party Transaction [Line Items] |  |  |  |  |
Other noncurrent liabilities | $ 12,069 |  | $ 12,069 |  | $ 10,972
Recognized share-based compensation expense | 168 | $ 181 | 307 | $ 305 |
NBCUniversal Media LLC [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Other noncurrent liabilities | 5,138 |  | 5,138 |  | $ 4,153
Recognized share-based compensation expense | 46 | $ 40 | 78 | $ 65 |
Carrying Value of Related Party Contractual Obligation [Member] | NBCUniversal Media LLC [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Other noncurrent liabilities | $ 383 |  | $ 383 |  |

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