Claim and Claim Adjustment Expense Reserves (Commercial - Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development) (Details) - Commercial - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Commercial	$ 74	$ 107	$ 33
General Liability	114	75	149
Workers' Compensation	(135)	(202)	(203)
Property and Other	(14)	4	(1)
Total pretax (favorable) unfavorable development	$ 39	$ (16)	$ (22)

Net prior year claim and allocated claim adjustment expense reserve development, Commercial Auto

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- Definition

Net prior year claim and allocated claim adjustment expense reserve development, General Liability

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- Definition

Net prior year claim and allocated claim adjustment expense reserve development, Property and Other

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- Definition

Net prior year claim and allocated claim adjustment expense reserve development, Workers' Compensation

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- Definition

Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve 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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