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Investments (Rollforward of expected credit-losses, AFS) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Jun. 30, 2023 | Dec. 31, 2022 | Jun. 30, 2022 | Dec. 31, 2021
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] |  |  |  |  |  |  |  |
Debt Securities, Available for sale, Allowance for Credit Loss | $ 158 | $ 147 | $ 158 | $ 147 | $ 193 | $ 169 | $ 78 | $ 14
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease) | 34 | 91 | 172 | 169 |  |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff | (1) | 0 | (5) | 0 |  |  |  |
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Foreign Currency Revaluation | 0 | (2) | 0 | (2) |  |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss, Recovery | $ (68) | $ (20) | $ (178) | $ (34) |  |  |  |

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