Insurance - Reinsurance information table including assumed, ceded, and recoveries (Details) - Property and casualty insurance - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effects of Reinsurance [Line Items]
Direct premiums written	$ 9,309	$ 8,774	$ 7,700
Reinsurance assumed	347	283	246
Reinsurance ceded	(2,964)	(2,851)	(2,373)
Net written premiums	6,692	6,206	5,573
Direct premiums earned	9,133	8,582	7,462
Reinsurance assumed	321	274	249
Reinsurance ceded	(2,923)	(2,771)	(2,307)
Net earned premiums	6,531	6,085	5,404
Reinsurance recoveries	$ 2,336	$ 2,065	$ 1,478

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 earned.

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

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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