Reinsurance - Effects of Reinsurance on Premiums Written and Earned (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct, written	$ 4,269	$ 4,251	$ 4,406
Assumed, written	294	299	293
Ceded, written	(1,087)	(1,105)	(1,117)
Net premiums, written	3,476	3,445	3,582
Direct, earned	4,292	4,286	4,460
Assumed, earned	294	299	293
Ceded, earned	(1,087)	(1,105)	(1,117)
Premiums earned, net	$ 3,499	$ 3,480	$ 3,636
Percentage of amount assumed to net	8.00%	9.00%	8.00%
Life insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct, written	$ 607	$ 656	$ 699
Assumed, written	1	1	1
Ceded, written	(444)	(478)	(493)
Direct, earned	607	656	699
Assumed, earned	1	1	1
Ceded, earned	(444)	(478)	(493)
Accident and health insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct, written	2,594	2,545	2,712
Assumed, written	260	277	288
Ceded, written	(510)	(512)	(537)
Direct, earned	2,594	2,545	2,712
Assumed, earned	260	277	288
Ceded, earned	(510)	(512)	(537)
Mortgage insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct, written	1,068	1,050	995
Assumed, written	33	21	4
Ceded, written	(133)	(115)	(87)
Direct, earned	1,091	1,085	1,049
Assumed, earned	33	21	4
Ceded, earned	$ (133)	$ (115)	$ (87)