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Investments (Investment and Other Income (Loss), Net) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Investment and Other Income (Loss), Net [Line Items] |  |  |
Equity in net income (losses) of investees, net | $ (505) | $ (364) | $ 107
Realized and unrealized gains (losses) on equity securities, net | 656 | (187) | (17)
Other income (loss), net | 287 | 326 | 331
Investment and other income (loss), net | 438 | (225) | 421
NBCUniversal Media LLC [Member] |  |  |
Investment and Other Income (Loss), Net [Line Items] |  |  |
Equity in net income (losses) of investees, net | (402) | (371) | (201)
Realized and unrealized gains (losses) on equity securities, net | 466 | (217) | 0
Other income (loss), net | 332 | 67 | 57
Investment and other income (loss), net | $ 396 | $ (521) | $ (144)

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