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Investments - Net appreciation (decline) recognized in net income (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | $ 117 | $ 178 | $ 585 | $ 15
Equity securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | (20) | 105 | 170 | (5)
Limited partnership interests carried at fair value |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | $ 137 | $ 73 | $ 415 | $ 20

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