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Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Segment Reporting Information [Line Items] |  |  |
Earnings before realized gains (losses) and income taxes | $ 1,124 | $ 1,113 | $ 1,239
Realized gains (losses) on securities | 0 | (36) | (116)
Realized loss on subsidiary | 0 | (4) | 0
Earnings before income taxes | 1,124 | 1,073 | 1,123
Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | 620 | 631 | 776
Investment and other income, net | 708 | 673 | 643
Earnings before realized gains (losses) and income taxes | 1,328 | 1,304 | 1,419
Other | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Earnings before realized gains (losses) and income taxes | (204) | (191) | (180)
Property and transportation | Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | 211 | 184 | 208
Specialty casualty | Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | 340 | 375 | 500
Specialty financial | Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | 134 | 110 | 114
Other specialty | Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | (59) | (36) | (42)
Other lines | Property and casualty insurance | Operating segments |  |  |
Segment Reporting Information [Line Items] |  |  |
Property and casualty insurance underwriting | $ (6) | $ (2) | $ (4)

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