Segments of Operations - Earnings before income taxes by segment and sub-segment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	$ 1,113	$ 1,239	$ 1,221
Realized gains (losses) on securities	(36)	(116)	110
Realized gains (losses) on subsidiaries	(4)	0	4
Earnings from continuing operations before income taxes	1,073	1,123	1,335
Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	631	776	733
Investment and other income, net	673	643	657
Earnings before realized gains (losses) and income taxes	1,304	1,419	1,390
Other
Segment Reporting Information [Line Items]
Earnings before realized gains (losses) and income taxes	(191)	(180)	(220)
Other \| Continuing operations
Segment Reporting Information [Line Items]
Earnings from real-estate related investments, net of DAC	0	0	51
Property and transportation \| Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	184	208	279
Specialty casualty \| Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	375	500	377
Specialty financial \| Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	110	114	96
Other specialty \| Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	(36)	(42)	(15)
Other lines \| Property and casualty insurance
Segment Reporting Information [Line Items]
Property and casualty insurance underwriting	$ (2)	$ (4)	$ (4)

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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.

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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.

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- Definition

Amount of gain (loss) on sale or disposal of equity in securities of subsidiaries.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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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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