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Claim and Claim Adjustment Expense Reserves (Net prior year development) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total pretax (favorable) unfavorable development	$ 17	$ 13	$ 33	$ 44
Specialty
Segment Reporting Information [Line Items]
Total pretax (favorable) unfavorable development	0	(5)	(8)	(9)
Commercial
Segment Reporting Information [Line Items]
Total pretax (favorable) unfavorable development	(3)	(2)	(11)	(17)
International
Segment Reporting Information [Line Items]
Total pretax (favorable) unfavorable development	(2)	0	(5)	15
Corporate & Other
Segment Reporting Information [Line Items]
Total pretax (favorable) unfavorable development	$ 22	$ 20	$ 57	$ 55

X

- Definition

Pretax Favorable Unfavorable Premium Development, excluding Life & Group

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- Definition

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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- Details

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- Details

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- Details

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