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Investments - Net appreciation (decline) recognized in net income (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | $ 266 | $ (445)
Equity securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | 125 | (417)
Limited partnership interests carried at fair value |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | $ 141 | $ (28)

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