Segment Information - Schedule of Revenues and Other Assets by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Premiums									$ 23,537	$ 25,564	$ 26,765
Adjusted Revenues	$ 7,177	$ 6,751	$ 6,560	$ 6,763	$ 6,526	$ 7,267	$ 7,436	$ 6,709	27,251	27,938	29,996
Net Investment Income									4,255	3,446	2,370
Net realized gains (losses)									(548)	(1,078)	827
Other income									7	6	34
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	1,116				1,132				1,116	1,132	1,153
North America
Segment Reporting Information [Line Items]
Adjusted Revenues									13,031	14,701	15,163
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	804				760				804	760	768
International
Segment Reporting Information [Line Items]
Adjusted Revenues									14,220	13,237	14,833
Real Estate and Other Fixed Assets, Net of Accumulated Depreciation	$ 312				$ 372				312	372	385
Reportable Segments
Segment Reporting Information [Line Items]
Premiums									23,457	25,091	25,340
Net Investment Income									3,060	3,022	2,382
All Other
Segment Reporting Information [Line Items]
Premiums									0	3	937
Net Investment Income									424	186	(122)
Business in Run-Off
Segment Reporting Information [Line Items]
Premiums									83	475	478
Elimination and consolidations
Segment Reporting Information [Line Items]
Premiums									(3)	(5)	10
Net Investment Income										(13)	14
North America Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Premiums									8,172	10,233	10,444
International Commercial | Reportable Segments
Segment Reporting Information [Line Items]
Premiums									8,145	7,964	7,701
Global Personal | Reportable Segments
Segment Reporting Information [Line Items]
Premiums									$ 7,140	$ 6,894	$ 7,195