Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022		Jun. 30, 2023	Jun. 30, 2022
Operating revenues
Net earned premiums	$ 2,347	$ 2,155	[1]	$ 4,595	$ 4,214	[1]
Net investment income	575	432	[1]	1,100	880	[1]
Non-insurance warranty revenue	407	392	[1]	814	774	[1]
Other revenues	7	6	[1]	14	13	[1]
Total operating revenues	3,336	2,985		6,523	5,881
Claims, Benefits and Expenses
Net incurred claims and benefits	1,772	1,594		3,418	3,066
Policyholders’ dividends	7	7		14	13
Amortization of deferred acquisition costs	403	374	[1]	782	718	[1]
Non-insurance warranty expense	384	367	[1]	768	721	[1]
Other insurance related expenses	318	275		623	566
Other expenses	59	82		119	145
Total claims, benefits and expenses	2,943	2,699	[1]	5,724	5,229
Core income (loss) before income tax	393	286		799	652
Income tax (expense) benefit on core income (loss)	(85)	(56)		(166)	(124)
Core income (loss)	308	230		633	528
Net investment gains (losses)	(32)	(59)		(67)	(70)
Income tax (expense) benefit on net investment gains (losses)	7	19		14	27
Net investment gains (losses), after tax	(25)	(40)		(53)	(43)
Net income (loss)	283	190		580	485
Operating Segments | Specialty
Operating revenues
Net earned premiums	812	794		1,609	1,566
Net investment income	142	100		271	203
Non-insurance warranty revenue	407	392		814	774
Other revenues	0	0		0	1
Total operating revenues	1,361	1,286		2,694	2,544
Claims, Benefits and Expenses
Net incurred claims and benefits	474	456		939	901
Policyholders’ dividends	2	2		3	3
Amortization of deferred acquisition costs	168	162		333	319
Non-insurance warranty expense	384	367		768	721
Other insurance related expenses	94	81		180	162
Other expenses	12	12		26	25
Total claims, benefits and expenses	1,134	1,080		2,249	2,131
Core income (loss) before income tax	227	206		445	413
Income tax (expense) benefit on core income (loss)	(50)	(45)		(97)	(89)
Core income (loss)	177	161		348	324
Operating Segments | Commercial
Operating revenues
Net earned premiums	1,120	974		2,166	1,878
Net investment income	165	113		314	231
Non-insurance warranty revenue	0	0		0	0
Other revenues	6	4		13	12
Total operating revenues	1,291	1,091		2,493	2,121
Claims, Benefits and Expenses
Net incurred claims and benefits	740	610		1,428	1,183
Policyholders’ dividends	5	5		11	10
Amortization of deferred acquisition costs	175	156		344	304
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	158	134		300	264
Other expenses	10	11		16	18
Total claims, benefits and expenses	1,088	916		2,099	1,779
Core income (loss) before income tax	203	175		394	342
Income tax (expense) benefit on core income (loss)	(44)	(37)		(84)	(72)
Core income (loss)	159	138		310	270
Operating Segments | International
Operating revenues
Net earned premiums	302	269		592	533
Net investment income	25	14		48	28
Non-insurance warranty revenue	0	0		0	0
Other revenues	1	1		1	0
Total operating revenues	328	284		641	561
Claims, Benefits and Expenses
Net incurred claims and benefits	185	160		374	318
Policyholders’ dividends	0	0		0	0
Amortization of deferred acquisition costs	60	56		105	95
Non-insurance warranty expense	0	0		0	0
Other insurance related expenses	35	30		82	77
Other expenses	(5)	13		(4)	14
Total claims, benefits and expenses	275	259		557	504
Core income (loss) before income tax	53	25		84	57
Income tax (expense) benefit on core income (loss)	(15)	(7)		(22)	(13)
Core income (loss)	38	18		62	44
Operating Segments | Life & Group
Operating revenues
Net earned premiums	113	118		228	238
Net investment income	229	201		443	413
Non-insurance warranty revenue	0	0		0	0
Other revenues	0	1		0	0
Total operating revenues	342	320		671	651
Claims, Benefits and Expenses
Net incurred claims and benefits	344	311		655	615
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	31	29		60	60
Other expenses	0	2		1	5
Total claims, benefits and expenses	375	342		716	680
Core income (loss) before income tax	(33)	(22)		(45)	(29)
Income tax (expense) benefit on core income (loss)	13	13		22	25
Core income (loss)	(20)	(9)		(23)	(4)
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0		0	(1)
Net investment income	14	4		24	5
Non-insurance warranty revenue	0	0		0	0
Other revenues	2	1		5	3
Total operating revenues	16	5		29	7
Claims, Benefits and Expenses
Net incurred claims and benefits	29	57		22	49
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	0	1		1	3
Other expenses	44	45		85	86
Total claims, benefits and expenses	73	103		108	138
Core income (loss) before income tax	(57)	(98)		(79)	(131)
Income tax (expense) benefit on core income (loss)	11	20		15	25
Core income (loss)	(46)	(78)		(64)	(106)
Eliminations
Operating revenues
Net earned premiums	0	0		0	0
Net investment income	0	0		0	0
Non-insurance warranty revenue	0	0		0	0
Other revenues	(2)	(1)		(5)	(3)
Total operating revenues	(2)	(1)		(5)	(3)
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	0	0		0	0
Other expenses	(2)	(1)		(5)	(3)
Total claims, benefits and expenses	(2)	(1)		(5)	(3)
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.