Business Segments (Balance Sheet Information) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Reinsurance receivables	$ 5,484	$ 4,478
Insurance receivables	2,974	2,640
Deferred acquisition costs	737	708
Goodwill	148	148
Deferred non-insurance warranty acquisition expense	3,476	3,068
Insurance reserves
Claim and claim adjustment expenses	24,174	22,706
Unearned premiums	5,761	5,119
Future policy benefits	13,236	13,318
Deferred non-insurance warranty revenue	4,503	4,023
Operating Segments | Specialty
Segment Reporting Information [Line Items]
Reinsurance receivables	1,200	886
Insurance receivables	1,136	1,052
Deferred acquisition costs	363	330
Goodwill	117	117
Deferred non-insurance warranty acquisition expense	3,476	3,068
Insurance reserves
Claim and claim adjustment expenses	6,433	5,748
Unearned premiums	3,001	2,635
Future policy benefits	0	0
Deferred non-insurance warranty revenue	4,503	4,023
Operating Segments | Commercial
Segment Reporting Information [Line Items]
Reinsurance receivables	923	848
Insurance receivables	1,488	1,254
Deferred acquisition costs	278	281
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	8,890	8,250
Unearned premiums	2,066	1,824
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | International
Segment Reporting Information [Line Items]
Reinsurance receivables	381	302
Insurance receivables	340	328
Deferred acquisition costs	96	97
Goodwill	31	31
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,280	2,091
Unearned premiums	585	546
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | Life & Group
Segment Reporting Information [Line Items]
Reinsurance receivables	401	390
Insurance receivables	6	4
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	3,754	3,743
Unearned premiums	109	114
Future policy benefits	13,236	13,318
Deferred non-insurance warranty revenue	0	0
Operating Segments | Corporate & Other
Segment Reporting Information [Line Items]
Reinsurance receivables	2,579	2,052
Insurance receivables	4	2
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,817	2,874
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