Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	$ 310	$ 376
Realized gains (losses) on securities	(46)	(15)
Earnings before income taxes	264	361
Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	154	207
Investment and other income, net	196	215
Earnings before realized gains (losses) and income taxes	350	422
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	(40)	(46)
Property and transportation \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	43	62
Specialty casualty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	88	124
Specialty financial \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	26	29
Other specialty \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	(2)	(7)
Other lines \| Property and Casualty Insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	$ (1)	$ (1)

Net investment income plus other income less other expenses.

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The net result for the period of deducting operating expenses from operating revenues (excluding realized gains (losses) on securities and subsidiaries) before income taxes.

+ References

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- Definition

Underwriting income (loss) for the property and casualty insurance segment, which is calculated as premiums earned less losses and loss adjustment expenses less commissions and other underwriting expenses.

+ References

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- Definition

Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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The net result for the period of deducting operating expenses from operating revenues.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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