Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Operating revenues
Net earned premiums	$ 2,759	$ 2,694	$ 5,460	$ 5,320
Net investment income	701	662	1,311	1,266
Non-insurance warranty revenue	367	398	741	795
Other revenues	7	9	17	18
Total operating revenues	3,834	3,763	7,529	7,399
Claims, Benefits and Expenses
Net incurred claims and benefits	2,160	2,075	4,323	4,092
Policyholders’ dividends	9	10	21	20
Amortization of deferred acquisition costs	481	469	957	940
Non-insurance warranty expense	356	384	712	769
Insurance related administrative expenses	343	337	675	658
Interest expense	33	31	66	63
Other segment items	42	31	80	73
Total claims, benefits and expenses	3,424	3,337	6,834	6,615
Income tax (expense) benefit on core income (loss)	(86)	(91)	(146)	(168)
Core income (loss)	324	335	549	616
Net investment gains (losses)	(5)	(46)	(23)	(55)
Income tax (expense) benefit on net investment gains (losses)	2	10	6	12
Net investment gains (losses), after tax	(3)	(36)	(17)	(43)
Net income (loss)	321	299	532	573
Operating Segments | Specialty
Operating revenues
Net earned premiums	878	862	1,730	1,692
Net investment income	171	170	313	321
Non-insurance warranty revenue	367	398	741	795
Other revenues	0	(1)	1	0
Total operating revenues	1,416	1,429	2,785	2,808
Claims, Benefits and Expenses
Net incurred claims and benefits	551	519	1,137	1,028
Policyholders’ dividends	3	3	7	5
Amortization of deferred acquisition costs	201	195	398	384
Non-insurance warranty expense	356	384	712	769
Insurance related administrative expenses	91	92	180	180
Interest expense	0	0	0	0
Other segment items	15	10	27	25
Total claims, benefits and expenses	1,217	1,203	2,461	2,391
Income tax (expense) benefit on core income (loss)	(42)	(49)	(68)	(90)
Core income (loss)	157	177	256	327
Operating Segments | Commercial
Operating revenues
Net earned premiums	1,441	1,402	2,853	2,782
Net investment income	246	206	436	383
Non-insurance warranty revenue	0	0	0	0
Other revenues	8	10	17	18
Total operating revenues	1,695	1,618	3,306	3,183
Claims, Benefits and Expenses
Net incurred claims and benefits	1,003	940	2,079	1,947
Policyholders’ dividends	6	7	14	15
Amortization of deferred acquisition costs	207	211	413	430
Non-insurance warranty expense	0	0	0	0
Insurance related administrative expenses	175	170	346	333
Interest expense	0	0	0	0
Other segment items	11	15	22	25
Total claims, benefits and expenses	1,402	1,343	2,874	2,750
Income tax (expense) benefit on core income (loss)	(61)	(57)	(88)	(91)
Core income (loss)	232	218	344	342
Operating Segments | International
Operating revenues
Net earned premiums	337	324	671	634
Net investment income	44	38	87	72
Non-insurance warranty revenue	0	0	0	0
Other revenues	0	0	0	0
Total operating revenues	381	362	758	706
Claims, Benefits and Expenses
Net incurred claims and benefits	209	195	413	387
Policyholders’ dividends	0	0	0	0
Amortization of deferred acquisition costs	73	63	146	126
Non-insurance warranty expense	0	0	0	0
Insurance related administrative expenses	45	43	88	83
Interest expense	0	0	0	0
Other segment items	0	(10)	2	(11)
Total claims, benefits and expenses	327	291	649	585
Income tax (expense) benefit on core income (loss)	(17)	(18)	(35)	(31)
Core income (loss)	37	53	74	90
Operating Segments | Life & Group
Operating revenues
Net earned premiums	103	106	206	212
Net investment income	230	235	454	461
Non-insurance warranty revenue	0	0	0	0
Other revenues	(1)	0	(1)	0
Total operating revenues	332	341	659	673
Claims, Benefits and Expenses
Net incurred claims and benefits	320	313	634	613
Policyholders’ dividends	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Non-insurance warranty expense	0	0	0	0
Insurance related administrative expenses	31	31	60	61
Interest expense	0	0	0	0
Other segment items	(1)	1	0	1
Total claims, benefits and expenses	350	345	694	675
Income tax (expense) benefit on core income (loss)	8	5	16	9
Core income (loss)	(10)	1	(19)	7
Operating Segments | Corporate & Other
Operating revenues
Net earned premiums	0	0	0	0
Net investment income	10	13	21	29
Non-insurance warranty revenue	0	0	0	0
Other revenues	3	3	6	6
Total operating revenues	13	16	27	35
Claims, Benefits and Expenses
Net incurred claims and benefits	77	108	60	117
Policyholders’ dividends	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Non-insurance warranty expense	0	0	0	0
Insurance related administrative expenses	1	1	1	1
Interest expense	33	31	66	63
Other segment items	20	18	35	39
Total claims, benefits and expenses	131	158	162	220
Income tax (expense) benefit on core income (loss)	26	28	29	35
Core income (loss)	(92)	(114)	(106)	(150)
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)	(3)	(6)	(6)
Total operating revenues	(3)	(3)	(6)	(6)
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
Insurance related administrative expenses	0	0	0	0
Interest expense	0	0	0	0
Other segment items	(3)	(3)	(6)	(6)
Total claims, benefits and expenses	(3)	(3)	(6)	(6)
Income tax (expense) benefit on core income (loss)	0	0	0	0
Core income (loss)	$ 0	$ 0	$ 0	$ 0