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Sales of Businesses - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Jun. 30, 2021 | Dec. 31, 2020 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Proceeds from sale of businesses |  |  |  |  | $ 3,547 | $ 0
Realized gains (losses) on subsidiaries | $ 0 |  |  | $ (30) | $ 4 | $ (30)
Neon Capital Limited |  |  |  |  |  |
Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Proceeds from sale of businesses |  |  | $ 6 |  |  |
Realized gains (losses) on subsidiaries |  | $ 4 |  | $ (30) |  |

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