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Investments (Net investment income) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021
Net Investment Income [Line Items] |  |  |  |
Gross investment income | $ 440 | $ 528 | $ 1,355 | $ 1,656
Investment expense | (18) | (15) | (53) | (48)
Net investment income | 422 | 513 | 1,302 | 1,608
Fixed maturity securities |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 454 | 425 | 1,324 | 1,278
Equity securities |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 2 | 4 | (7) | 53
Limited partnership investments |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | (35) | 85 | (11) | 274
Mortgage loans |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 13 | 13 | 40 | 42
Short term investments |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 4 | 1 | 6 | 1
Trading portfolio |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 1 | 1 | 2 | 8
Other |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Gross investment income | 1 | (1) | 1 | 0
Common Stock |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income (loss) recognized due to the change in fair value of common stock held as of September 30, 2022 and 2021 | $ (18) | $ (7) | $ (38) | $ 11

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