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Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Net Investment Income [Line Items] |  |  |  |
Investment income | $ 193 | $ 203 | $ 397 | $ 425
Equity in earnings of partnerships and similar investments | 14 | 28 | 39 | 85
Investment expenses | (5) | (5) | (11) | (10)
Net investment income | 188 | 198 | 386 | 415
Fixed maturities: | Net investment income |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Investment income | 136 | 124 | 270 | 243
Fixed maturities: | Net investment income |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Change in fair value of fixed maturity securities | 0 | 7 | 0 | 10
Equity securities | Net investment income |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Dividends | 7 | 9 | 14 | 18
Change in fair value of equity securities | 9 | 13 | 25 | 29
Other |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Investment income | $ 27 | $ 22 | $ 49 | $ 40

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