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Investments - Net appreciation (decline) recognized in net income (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | $ 269 | $ 170 | $ 504 | $ (168)
Equity securities |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | 132 | 196 | 226 | (114)
Limited partnership interests carried at fair value |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Total | $ 137 | $ (26) | $ 278 | $ (54)

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