Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022		Sep. 30, 2023	Sep. 30, 2022
Operating revenues
Net earned premiums	$ 2,406	$ 2,221	[1]	$ 7,001	$ 6,435	[1]
Net investment income	553	422	[1]	1,653	1,302	[1]
Non-insurance warranty revenue	407	399	[1]	1,221	1,173	[1]
Other revenues	8	11	[1]	22	24	[1]
Total operating revenues	3,374	3,053		9,897	8,934
Claims, Benefits and Expenses
Net incurred claims and benefits	1,818	1,873		5,236	4,939
Policyholders’ dividends	8	7		22	20
Amortization of deferred acquisition costs	426	383	[1]	1,208	1,101	[1]
Non-insurance warranty expense	386	371	[1]	1,154	1,092	[1]
Other insurance related expenses	294	297		917	863
Other expenses	78	77		197	222
Total claims, benefits and expenses	3,010	3,008	[1]	8,734	8,237	[1]
Core income (loss) before income tax	364	45		1,163	697
Income tax (expense) benefit on core income (loss)	(75)	(2)		(241)	(126)
Core income (loss)	289	43		922	571
Net investment gains (losses)	(38)	(96)		(105)	(166)
Income tax (expense) benefit on net investment gains (losses)	7	11		21	38
Net investment gains (losses), after tax	(31)	(85)		(84)	(128)
Net income (loss)	258	(42)		838	443
Operating Segments | Specialty
Operating revenues
Net earned premiums	829	810		2,438	2,376
Net investment income	136	102		407	305
Non-insurance warranty revenue	407	399		1,221	1,173
Other revenues	0	(1)		0	0
Total operating revenues	1,372	1,310		4,066	3,854
Claims, Benefits and Expenses
Net incurred claims and benefits	480	459		1,419	1,360
Policyholders’ dividends	2	2		5	5
Amortization of deferred acquisition costs	175	169		508	488
Non-insurance warranty expense	386	371		1,154	1,092
Other insurance related expenses	89	88		269	250
Other expenses	13	15		39	40
Total claims, benefits and expenses	1,145	1,104		3,394	3,235
Core income (loss) before income tax	227	206		672	619
Income tax (expense) benefit on core income (loss)	(49)	(45)		(146)	(134)
Core income (loss)	178	161		526	485
Operating Segments | Commercial
Operating revenues
Net earned premiums	1,170	1,023		3,336	2,901
Net investment income	156	112		470	343
Non-insurance warranty revenue	0	0		0	0
Other revenues	9	13		22	25
Total operating revenues	1,335	1,148		3,828	3,269
Claims, Benefits and Expenses
Net incurred claims and benefits	807	733		2,235	1,916
Policyholders’ dividends	6	5		17	15
Amortization of deferred acquisition costs	188	163		532	467
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	156	145		456	409
Other expenses	11	3		27	21
Total claims, benefits and expenses	1,168	1,049		3,267	2,828
Core income (loss) before income tax	167	99		561	441
Income tax (expense) benefit on core income (loss)	(34)	(19)		(118)	(91)
Core income (loss)	133	80		443	350
Operating Segments | International
Operating revenues
Net earned premiums	296	270		888	803
Net investment income	26	16		74	44
Non-insurance warranty revenue	0	0		0	0
Other revenues	(1)	0		0	0
Total operating revenues	321	286		962	847
Claims, Benefits and Expenses
Net incurred claims and benefits	178	169		552	487
Policyholders’ dividends	0	0		0	0
Amortization of deferred acquisition costs	63	51		168	146
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	20	35		102	112
Other expenses	6	11		2	25
Total claims, benefits and expenses	267	266		824	770
Core income (loss) before income tax	54	20		138	77
Income tax (expense) benefit on core income (loss)	(14)	(1)		(36)	(14)
Core income (loss)	40	19		102	63
Operating Segments | Life & Group
Operating revenues
Net earned premiums	112	118		340	356
Net investment income	216	187		659	600
Non-insurance warranty revenue	0	0		0	0
Other revenues	0	0		0	0
Total operating revenues	328	305		999	956
Claims, Benefits and Expenses
Net incurred claims and benefits	343	525		998	1,140
Policyholders’ dividends	0	0		0	0
Amortization of deferred acquisition costs	0	0		0	0
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	29	29		89	89
Other expenses	(1)	2		0	7
Total claims, benefits and expenses	371	556		1,087	1,236
Core income (loss) before income tax	(43)	(251)		(88)	(280)
Income tax (expense) benefit on core income (loss)	14	59		36	84
Core income (loss)	(29)	(192)		(52)	(196)
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0		0	(1)
Net investment income	19	5		43	10
Non-insurance warranty revenue	0	0		0	0
Other revenues	2	1		7	4
Total operating revenues	21	6		50	13
Claims, Benefits and Expenses
Net incurred claims and benefits	10	(13)		32	36
Policyholders’ dividends	0	0		0	0
Amortization of deferred acquisition costs	0	0		0	0
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	1	1		2	4
Other expenses	51	47		136	133
Total claims, benefits and expenses	62	35		170	173
Core income (loss) before income tax	(41)	(29)		(120)	(160)
Income tax (expense) benefit on core income (loss)	8	4		23	29
Core income (loss)	(33)	(25)		(97)	(131)
Eliminations
Operating revenues
Net earned premiums	(1)	0		(1)	0
Net investment income	0	0		0	0
Non-insurance warranty revenue	0	0		0	0
Other revenues	(2)	(2)		(7)	(5)
Total operating revenues	(3)	(2)		(8)	(5)
Claims, Benefits and Expenses
Net incurred claims and benefits	0	0		0	0
Policyholders’ dividends	0	0		0	0
Amortization of deferred acquisition costs	0	0		0	0
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	(1)	(1)		(1)	(1)
Other expenses	(2)	(1)		(7)	(4)
Total claims, benefits and expenses	(3)	(2)		(8)	(5)
Core income (loss) before income tax	0	0		0	0
Income tax (expense) benefit on core income (loss)	0	0		0	0
Core income (loss)	$ 0	$ 0		$ 0	$ 0

[1] As of January 1, 2023, the Company adopted ASU 2018-12, Financial Services-Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts (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.