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Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Segment Reporting Information [Line Items] |  |
Earnings before realized gains (losses) and income taxes | $ 290 | $ 310
Realized gains (losses) on securities | 14 | (46)
Earnings before income taxes | 304 | 264
Operating Segments | Property and Casualty Insurance |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | 153 | 154
Investment and other income, net | 187 | 196
Earnings before realized gains (losses) and income taxes | 340 | 350
Operating Segments | Property and Casualty Insurance | Property and transportation |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | 56 | 43
Operating Segments | Property and Casualty Insurance | Specialty casualty |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | 74 | 88
Operating Segments | Property and Casualty Insurance | Specialty financial |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | 33 | 26
Operating Segments | Property and Casualty Insurance | Other specialty |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | (9) | (2)
Operating Segments | Property and Casualty Insurance | Other lines |  |
Segment Reporting Information [Line Items] |  |
Property and casualty insurance underwriting | (1) | (1)
Operating Segments | Other |  |
Segment Reporting Information [Line Items] |  |
Earnings before realized gains (losses) and income taxes | $ (50) | $ (40)

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