Reinsurance - Consolidated Property Casualty Insurance Assumed and Ceded Business (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Property Casualty Insurance Assumed And Ceded Business
Earned premiums	$ 2,071	$ 1,918
Incurred loss and loss expenses	1,349	1,398
Consolidated Property And Casualty Insurance
Property Casualty Insurance Assumed And Ceded Business
Direct written premiums	2,125	1,859
Assumed written premiums	239	244
Ceded written premiums	(116)	(84)
Net written premiums	2,248	2,019
Direct earned premiums	1,934	1,760
Assumed earned premiums	152	159
Ceded earned premiums	(94)	(78)
Earned premiums	1,992	1,841
Direct incurred loss and loss expenses	1,193	1,299
Assumed incurred loss and loss expenses	76	76
Ceded incurred loss and loss expenses	1	(58)
Incurred loss and loss expenses	$ 1,270	$ 1,317

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Amount of earned premiums assumed from other entities.

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Amount of written premiums assumed from other entities.

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Amount of earned premiums ceded to other entities.

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Amount of written premiums ceded to other entities.

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums written.

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

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Amount of policy benefits and costs incurred for policies assumed.

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