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Marketable and Other Securities - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Marketable Securities [Line Items] |  |  |
Sales proceeds from investments classified as available-for-sale and sold prior to maturity | $ 1,900 | $ 4,500 | $ 4,300
Lyft, Inc. | Interest Income and Other Non-Operating Income |  |  |
Marketable Securities [Line Items] |  |  |
Unrealized gain (loss) on securities |  |  | $ 142

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