Business Segments (Balance sheet information) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Reinsurance receivables	$ 5,721	$ 5,484
Insurance receivables	3,014	2,974
Deferred acquisition costs	787	737
Goodwill	142	148
Deferred non-insurance warranty acquisition expense	3,653	3,476
Insurance reserves
Claim and claim adjustment expenses	24,700	24,174
Unearned premiums	6,195	5,761
Future policy benefits	10,454	13,236
Deferred non-insurance warranty revenue	4,706	4,503
Operating Segments | Specialty
Segment Reporting Information [Line Items]
Reinsurance receivables	1,511	1,200
Insurance receivables	1,061	1,136
Deferred acquisition costs	379	363
Goodwill	117	117
Deferred non-insurance warranty acquisition expense	3,653	3,476
Insurance reserves
Claim and claim adjustment expenses	6,925	6,433
Unearned premiums	3,144	3,001
Future policy benefits	0	0
Deferred non-insurance warranty revenue	4,706	4,503
Operating Segments | Commercial
Segment Reporting Information [Line Items]
Reinsurance receivables	952	923
Insurance receivables	1,640	1,488
Deferred acquisition costs	315	278
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	9,172	8,890
Unearned premiums	2,364	2,066
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | International
Segment Reporting Information [Line Items]
Reinsurance receivables	385	381
Insurance receivables	309	340
Deferred acquisition costs	93	96
Goodwill	25	31
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,262	2,280
Unearned premiums	576	585
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | Life & Group
Segment Reporting Information [Line Items]
Reinsurance receivables	453	401
Insurance receivables	4	6
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	3,645	3,754
Unearned premiums	111	109
Future policy benefits	10,454	13,236
Deferred non-insurance warranty revenue	0	0
Operating Segments | Corporate & Other
Segment Reporting Information [Line Items]
Reinsurance receivables	2,420	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	2,696	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