Segments of Operations - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 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%	5.00%	7.00%
Net earned premiums	$ 5,404	$ 5,099	$ 5,185
Net investment income	730	461	532
Property and casualty insurance
Segment Reporting Information [Line Items]
Net earned premiums	5,404	5,099	5,185
Net investment income	663	399	472
Property and casualty insurance underwriting	733	224	212
Investment and other income, net	657	360	437
Property and casualty insurance \| Other lines
Segment Reporting Information [Line Items]
Net earned premiums	0	200	0
Property and casualty insurance underwriting	(4)	(202)	(113)
Special A&E charges		47	18
Other
Segment Reporting Information [Line Items]
Loss on the retirement of debt		5	5
Special charges to increase asbestos and environmental reserves		21	11
Special A&E charges
Segment Reporting Information [Line Items]
Special A&E charges	$ 0	47	18
Special A&E charges \| Property and casualty insurance \| Other lines
Segment Reporting Information [Line Items]
Special A&E charges		47	$ 18
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]
Percent of foreign sales attributable to Neon		50.00%	66.67%
Net earned premiums			$ 384
Net investment income		$ (5)
Property and casualty insurance underwriting		(135)	(36)
Special charges related to the exit of certain lines of business within subsidiaries			$ 76
Investment and other income, net		$ (10)

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

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Property and casualty insurance revenues derived from customers of foreign countries by subsidiary

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Net investment income plus other income less other expenses.

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Special charges to increase asbestos and environmental reserves

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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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