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Marketable and Other Securities - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018
Marketable Securities [Line Items] |  |  |  |  |
Sale proceeds from investments classified as available-for-sale and sold prior to maturity | $ 535 | $ 1,700 | $ 1,600 | $ 3,600 |
Lyft, Inc. [Member] | Level 1 [Member] | Other current assets [Member] |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Fair value of equity securities | 679 |  | 679 |  |
Lyft, Inc. [Member] | Level 1 [Member] | Interest Income and Other Non-Operating Income [Member] |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Unrealized gain (loss) on securities | $ (291) |  | $ 71 |  |
Lyft, Inc. [Member] | Level 3 [Member] | Other assets [Member] |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Fair value of equity securities |  |  |  |  | $ 884
Lyft, Inc. [Member] | Level 3 [Member] | Interest Income and Other Non-Operating Income [Member] |  |  |  |  |
Marketable Securities [Line Items] |  |  |  |  |
Unrealized gain (loss) on securities |  |  |  | $ 142 |

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