Segment Information - Reconciliation of Assets From Segment To Consolidated (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Segment Reporting [Line Items]
Total assets	$ 87,983	$ 86,029
Operating Segments [Member]
Segment Reporting [Line Items]
Total assets	83,065	81,831
Operating Segments [Member] \| P&C Business Insurance
Segment Reporting [Line Items]
Total assets	59,398	57,468
Operating Segments [Member] \| P&C Personal Insurance
Segment Reporting [Line Items]
Total assets	6,067	6,445
Operating Segments [Member] \| Property & Casualty Other Operations [Member]
Segment Reporting [Line Items]
Total assets	4,339	4,354
Operating Segments [Member] \| Employee Benefits [Member]
Segment Reporting [Line Items]
Total assets	13,261	13,564
Corporate, Non-Segment [Member]
Segment Reporting [Line Items]
Total assets	$ 4,918	$ 4,198

Amount of asset recognized for present right to economic benefit.

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+ Details

- 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