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Investments - Net appreciation (decline) recognized in net income (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | $ 728 | $ 1,222
Equity securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | 478 | 1,073
Limited partnership interests carried at fair value |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Total | $ 250 | $ 149

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