Business Segments (Balance Sheet Information) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022		Jun. 30, 2022	Dec. 31, 2020
Segment Reporting Information [Line Items]
Reinsurance receivables	$ 5,603	$ 5,438
Insurance receivables	3,551	3,187
Deferred acquisition costs	885	806	[1]
Goodwill	146	144	[1]
Deferred non-insurance warranty acquisition expense	3,689	3,671	[1]
Insurance reserves
Claim and claim adjustment expenses	22,802	22,120	[1]
Unearned premiums	6,978	6,374	[1]
Future policy benefits	13,666	13,480	[1]	$ 14,157	$ 19,132
Deferred non-insurance warranty revenue	4,735	4,714	[1]
Operating Segments | Specialty
Segment Reporting Information [Line Items]
Reinsurance receivables	1,530	1,384
Insurance receivables	1,034	1,082
Deferred acquisition costs	395	381
Goodwill	117	117
Deferred non-insurance warranty acquisition expense	3,689	3,671
Insurance reserves
Claim and claim adjustment expenses	7,183	6,878
Unearned premiums	3,194	3,193
Future policy benefits	0	0
Deferred non-insurance warranty revenue	4,735	4,714
Operating Segments | Commercial
Segment Reporting Information [Line Items]
Reinsurance receivables	1,153	1,062
Insurance receivables	2,050	1,728
Deferred acquisition costs	359	321
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	9,674	9,395
Unearned premiums	2,882	2,425
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | International
Segment Reporting Information [Line Items]
Reinsurance receivables	445	414
Insurance receivables	462	369
Deferred acquisition costs	131	104
Goodwill	29	27
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,583	2,403
Unearned premiums	790	653
Future policy benefits	0	0
Deferred non-insurance warranty revenue	0	0
Operating Segments | Life & Group
Segment Reporting Information [Line Items]
Reinsurance receivables	100	101
Insurance receivables	4	8
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	688	695
Unearned premiums	112	103
Future policy benefits	13,666	13,480
Deferred non-insurance warranty revenue	0	0
Operating Segments | Corporate & Other
Segment Reporting Information [Line Items]
Reinsurance receivables	2,375	2,477
Insurance receivables	1	0
Deferred acquisition costs	0	0
Goodwill	0	0
Deferred non-insurance warranty acquisition expense	0	0
Insurance reserves
Claim and claim adjustment expenses	2,674	2,749
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

[1] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Condensed Consolidated Financial Statements for additional information.