Segment Information - Schedule of Revenues and Other Assets by Geographic Area (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Premiums	$ 23,751	$ 23,537	$ 25,564
Net Investment Income	4,215	4,255	3,446
Total net realized losses	(1,202)	(548)	(1,078)
Other income	11	7	6
Revenues	26,775	27,251	27,938
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	1,369	1,116	1,132
North America
Segment Reporting Information [Line Items]
Revenues	12,699	13,031	14,701
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	1,034	804	760
International
Segment Reporting Information [Line Items]
Revenues	14,076	14,220	13,237
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	335	312	372
Reportable Segments
Segment Reporting Information [Line Items]
Premiums	23,678	23,457	25,091
Net Investment Income	3,433	3,060	3,022
All Other
Segment Reporting Information [Line Items]
Premiums	0	0	3
Net Investment Income	346	424	186
Business in Run-Off
Segment Reporting Information [Line Items]
Premiums	76	83	475
Elimination and consolidations
Segment Reporting Information [Line Items]
Premiums	(3)	(3)	(5)
Net Investment Income	(1)	0	(13)
North America Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Premiums	8,626	8,172	10,233
International Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Premiums	8,580	8,145	7,964
Global Personal | Reportable Segments
Segment Reporting Information [Line Items]
Premiums	$ 6,472	$ 7,140	$ 6,894