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Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Segment Reporting Information [Line Items] |  |  |  |
Earnings before realized gains (losses) and income taxes | $ 273 | $ 257 | $ 563 | $ 567
Realized gains (losses) on securities | (2) | (2) | 12 | (48)
Earnings before income taxes | 271 | 255 | 575 | 519
Operating Segments | Property and Casualty Insurance |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | 150 | 124 | 303 | 278
Investment and other income, net | 169 | 175 | 356 | 371
Earnings before realized gains (losses) and income taxes | 319 | 299 | 659 | 649
Operating Segments | Property and Casualty Insurance | Property and transportation |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | 39 | 32 | 95 | 75
Operating Segments | Property and Casualty Insurance | Specialty casualty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | 108 | 95 | 182 | 183
Operating Segments | Property and Casualty Insurance | Specialty financial |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | 25 | 10 | 58 | 36
Operating Segments | Property and Casualty Insurance | Other specialty |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | (21) | (14) | (30) | (16)
Operating Segments | Property and Casualty Insurance | Other lines |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Property and casualty insurance underwriting | (1) | 1 | (2) | 0
Operating Segments | Other |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Earnings before realized gains (losses) and income taxes | $ (46) | $ (42) | $ (96) | $ (82)

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