Segments of Operations - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of segments \| segment	2
Percent of total revenue derived from sales of property and casualty insurance outside of the United States	4.00%	4.00%	5.00%
Net earned premiums	$ 6,085	$ 5,404	$ 5,099
Net investment income	717	730	461
Property and casualty insurance
Segment Reporting Information [Line Items]
Net earned premiums	6,085	5,404	5,099
Net investment income	683	663	399
Property and casualty insurance underwriting	776	733	224
Investment and other income, net	643	657	360
Property and casualty insurance \| Other lines
Segment Reporting Information [Line Items]
Net earned premiums	0	0	200
Property and casualty insurance underwriting	(4)	(4)	(202)
Special A&E charges			47
Other
Segment Reporting Information [Line Items]
Loss on the retirement of debt	(9)		(5)
Liability for Asbestos and Environmental Claims, Net, Period Increase (Decrease)			21
Special A&E charges
Segment Reporting Information [Line Items]
Special A&E charges	$ 0	$ 0	47
Special A&E charges \| Property and casualty insurance \| Other lines
Segment Reporting Information [Line Items]
Special A&E charges			47
Neon Capital Limited
Segment Reporting Information [Line Items]
Net investment income			(5)
Neon Capital Limited \| Property and casualty insurance \| Other lines
Segment Reporting Information [Line Items]
Net investment income			(5)
Property and casualty insurance underwriting			(135)
Investment and other income, net			$ (10)

Property and casualty insurance revenues derived from customers of foreign countries.

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Net investment income plus other income less other expenses.

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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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Amount, after effects of reinsurance, of expense for claims incurred and costs incurred in the claim settlement process attributable to asbestos and environmental claims.

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of property and casualty premiums earned.

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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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