Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating revenues
Net earned premiums	$ 2,498	$ 2,347	$ 4,939	$ 4,595
Net investment income	618	575	1,227	1,100
Non-insurance warranty revenue	404	407	811	814
Other revenues	9	7	18	14
Total operating revenues	3,529	3,336	6,995	6,523
Claims, Benefits and Expenses
Net incurred claims and benefits	1,874	1,772	3,672	3,418
Policyholders’ dividends	8	7	17	14
Amortization of deferred acquisition costs	435	403	879	782
Non-insurance warranty expense	388	384	782	768
Other insurance related expenses	329	318	616	623
Other expenses	83	59	168	119
Total claims, benefits and expenses	3,117	2,943	6,134	5,724
Core income (loss) before income tax	412	393	861	799
Income tax (expense) benefit on core income (loss)	(86)	(85)	(180)	(166)
Core income (loss)	326	308	681	633
Net investment gains (losses)	(10)	(32)	(32)	(67)
Income tax (expense) benefit on net investment gains (losses)	1	7	6	14
Net investment gains (losses), after tax	(9)	(25)	(26)	(53)
Net income (loss)	317	283	655	580
Operating Segments | Specialty
Operating revenues
Net earned premiums	831	812	1,645	1,609
Net investment income	154	142	304	271
Non-insurance warranty revenue	404	407	811	814
Other revenues	(1)	0	0	0
Total operating revenues	1,388	1,361	2,760	2,694
Claims, Benefits and Expenses
Net incurred claims and benefits	492	474	969	939
Policyholders’ dividends	3	2	5	3
Amortization of deferred acquisition costs	180	168	358	333
Non-insurance warranty expense	388	384	782	768
Other insurance related expenses	96	94	177	180
Other expenses	13	12	28	26
Total claims, benefits and expenses	1,172	1,134	2,319	2,249
Core income (loss) before income tax	216	227	441	445
Income tax (expense) benefit on core income (loss)	(47)	(50)	(95)	(97)
Core income (loss)	169	177	346	348
Operating Segments | Commercial
Operating revenues
Net earned premiums	1,247	1,120	2,449	2,166
Net investment income	175	165	351	314
Non-insurance warranty revenue	0	0	0	0
Other revenues	10	6	18	13
Total operating revenues	1,432	1,291	2,818	2,493
Claims, Benefits and Expenses
Net incurred claims and benefits	846	740	1,674	1,428
Policyholders’ dividends	5	5	12	11
Amortization of deferred acquisition costs	199	175	399	344
Non-insurance warranty expense	0	0	0	0
Other insurance related expenses	158	158	296	300
Other expenses	13	10	25	16
Total claims, benefits and expenses	1,221	1,088	2,406	2,099
Core income (loss) before income tax	211	203	412	394
Income tax (expense) benefit on core income (loss)	(44)	(44)	(87)	(84)
Core income (loss)	167	159	325	310
Operating Segments | International
Operating revenues
Net earned premiums	311	302	626	592
Net investment income	32	25	63	48
Non-insurance warranty revenue	0	0	0	0
Other revenues	0	1	0	1
Total operating revenues	343	328	689	641
Claims, Benefits and Expenses
Net incurred claims and benefits	184	185	373	374
Policyholders’ dividends	0	0	0	0
Amortization of deferred acquisition costs	56	60	122	105
Non-insurance warranty expense	0	0	0	0
Other insurance related expenses	46	35	85	82
Other expenses	1	(5)	3	(4)
Total claims, benefits and expenses	287	275	583	557
Core income (loss) before income tax	56	53	106	84
Income tax (expense) benefit on core income (loss)	(12)	(15)	(25)	(22)
Core income (loss)	44	38	81	62
Operating Segments | Life & Group
Operating revenues
Net earned premiums	109	113	219	228
Net investment income	239	229	470	443
Non-insurance warranty revenue	0	0	0	0
Other revenues	0	0	0	0
Total operating revenues	348	342	689	671
Claims, Benefits and Expenses
Net incurred claims and benefits	325	344	637	655
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	31	58	60
Other expenses	1	0	1	1
Total claims, benefits and expenses	355	375	696	716
Core income (loss) before income tax	(7)	(33)	(7)	(45)
Income tax (expense) benefit on core income (loss)	6	13	11	22
Core income (loss)	(1)	(20)	4	(23)
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0	0	0
Net investment income	18	14	39	24
Non-insurance warranty revenue	0	0	0	0
Other revenues	3	2	6	5
Total operating revenues	21	16	45	29
Claims, Benefits and Expenses
Net incurred claims and benefits	27	29	19	22
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	1
Other expenses	58	44	117	85
Total claims, benefits and expenses	85	73	136	108
Core income (loss) before income tax	(64)	(57)	(91)	(79)
Income tax (expense) benefit on core income (loss)	11	11	16	15
Core income (loss)	(53)	(46)	(75)	(64)
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	(3)	(2)	(6)	(5)
Total operating revenues	(3)	(2)	(6)	(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	0	0	0	0
Other expenses	(3)	(2)	(6)	(5)
Total claims, benefits and expenses	(3)	(2)	(6)	(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