Segment Information - Reconciliation of Assets From Segment To Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Total assets	$ 84,995	$ 80,917
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	81,777	77,905
Operating Segments [Member] | P&C Business Insurance
Segment Reporting Information [Line Items]
Total assets	56,873	53,296
Operating Segments [Member] | P&C Personal Insurance
Segment Reporting Information [Line Items]
Total assets	6,550	6,034
Operating Segments [Member] | Property & Casualty Other Operations [Member]
Segment Reporting Information [Line Items]
Total assets	4,165	4,312
Operating Segments [Member] | Employee Benefits [Member]
Segment Reporting Information [Line Items]
Total assets	13,404	13,502
Operating Segments [Member] | Hartford Funds [Member]
Segment Reporting Information [Line Items]
Total assets	785	761
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total assets	$ 3,218	$ 3,012