Business Segments (Balance Sheet Information) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Reinsurance receivables	$ 5,438	$ 5,484
Insurance receivables	3,187	2,974
Deferred acquisition costs	806	737
Goodwill	144	148
Deferred non-insurance warranty acquisition expense	3,671	3,476
Insurance reserves
Claim and claim adjustment expenses	25,099	24,174
Unearned premiums	6,374	5,761
Future policy benefits	10,151	13,236
Deferred non-insurance warranty revenue	4,714	4,503
Operating Segments | Specialty
Segment Reporting Information [Line Items]
Reinsurance receivables	1,384	1,200
Insurance receivables	1,082	1,136
Deferred acquisition costs	381	363
Goodwill	117	117
Deferred non-insurance warranty acquisition expense	3,671	3,476
Insurance reserves
Claim and claim adjustment expenses	6,878	6,433
Unearned premiums	3,193	3,001
Future policy benefits	0	0
Deferred non-insurance warranty revenue	4,714	4,503
Operating Segments | Commercial
Segment Reporting Information [Line Items]
Reinsurance receivables	1,062	923
Insurance receivables	1,728	1,488
Deferred acquisition costs	321	278
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	9,395	8,890
Unearned premiums	2,425	2,066
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | International
Segment Reporting Information [Line Items]
Reinsurance receivables	414	381
Insurance receivables	369	340
Deferred acquisition costs	104	96
Goodwill	27	31
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,403	2,280
Unearned premiums	653	585
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | Life & Group
Segment Reporting Information [Line Items]
Reinsurance receivables	101	401
Insurance receivables	8	6
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	3,674	3,754
Unearned premiums	103	109
Future policy benefits	10,151	13,236
Deferred non-insurance warranty revenue	0	0
Operating Segments | Corporate & Other
Segment Reporting Information [Line Items]
Reinsurance receivables	2,477	2,579
Insurance receivables	0	4
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,749	2,817
Unearned premiums	0	0
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Eliminations
Segment Reporting Information [Line Items]
Reinsurance receivables	0	0
Insurance receivables	0	0
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	0	0
Unearned premiums	0	0
Future policy benefits	0	0
Deferred non-insurance warranty revenue	$ 0	$ 0