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Investments (Net investment income) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Net Investment Income [Line Items] |  |
Gross investment income | $ 626 | $ 630
Investment expense | (22) | (21)
Net investment income | 604 | 609
Fixed maturity securities |  |
Net Investment Income [Line Items] |  |
Gross investment income | 522 | 502
Equity securities |  |
Net Investment Income [Line Items] |  |
Gross investment income | 6 | 22
Limited partnership investments |  |
Net Investment Income [Line Items] |  |
Gross investment income | 56 | 54
Mortgage loans |  |
Net Investment Income [Line Items] |  |
Gross investment income | 16 | 15
Short-term investments |  |
Net Investment Income [Line Items] |  |
Gross investment income | 19 | 28
Trading portfolio |  |
Net Investment Income [Line Items] |  |
Gross investment income | 1 | 1
Other |  |
Net Investment Income [Line Items] |  |
Gross investment income | 6 | 8
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 March 31, 2025 and 2024 | $ (4) | $ 13

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