Schedule III (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	$ 2,065	$ 2,117
Liability for Unpaid Losses and Loss Adjustment Expenses, Future Policy Benefits	70,485	71,860
Unearned Premiums	17,232	17,375
Policy and Contract Claims	31	23
Premiums	23,537	25,564	$ 26,765
Net Investment Income	4,255	3,446	2,370
Losses and Loss Expenses Incurred	14,567	15,393	15,461
Amortization of Deferred Policy Acquisition Costs	3,425	3,771	3,545
Other Operating Expenses	5,529	5,399	6,159
Net Premiums Written	23,902	27,206	26,760
Net Investment Income	4,255	3,446	2,370
Reportable Segments
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Net Investment Income	3,060	3,022	2,382
All Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	(95)	(61)
Liability for Unpaid Losses and Loss Adjustment Expenses, Future Policy Benefits	6,759	6,409
Unearned Premiums	183	276
Policy and Contract Claims	31	23
Premiums	80	473	1,425
Net Investment Income	1,195	424	(12)
Losses and Loss Expenses Incurred	529	618	54
Amortization of Deferred Policy Acquisition Costs	12	148	12
Other Operating Expenses	1,440	1,055	1,807
Net Premiums Written	0	487	1,248
North America Commercial | Reportable Segments
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	379	317
Liability for Unpaid Losses and Loss Adjustment Expenses, Future Policy Benefits	39,619	39,758
Unearned Premiums	5,936	5,660
Policy and Contract Claims	0	0
Premiums	8,172	10,233	10,444
Losses and Loss Expenses Incurred	5,713	6,323	7,218
Amortization of Deferred Policy Acquisition Costs	824	1,371	1,381
Other Operating Expenses	1,087	1,184	1,101
Net Premiums Written	8,452	11,432	10,899
International Commercial | Reportable Segments
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	718	691
Liability for Unpaid Losses and Loss Adjustment Expenses, Future Policy Benefits	16,208	17,354
Unearned Premiums	5,773	5,789
Policy and Contract Claims	0	0
Premiums	8,145	7,964	7,701
Losses and Loss Expenses Incurred	4,463	4,641	4,301
Amortization of Deferred Policy Acquisition Costs	1,018	943	938
Other Operating Expenses	1,437	1,378	1,323
Net Premiums Written	8,364	8,168	7,877
Global Personal | Reportable Segments
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred Policy Acquisition Costs	1,063	1,170
Liability for Unpaid Losses and Loss Adjustment Expenses, Future Policy Benefits	7,899	8,339
Unearned Premiums	5,340	5,650
Policy and Contract Claims	0	0
Premiums	7,140	6,894	7,195
Losses and Loss Expenses Incurred	3,862	3,811	3,888
Amortization of Deferred Policy Acquisition Costs	1,571	1,309	1,214
Other Operating Expenses	1,565	1,782	1,928
Net Premiums Written	$ 7,086	$ 7,119	$ 6,736