Debt - Schedule of Aggregate Carrying Value of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 15, 2026	Dec. 31, 2025
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Total debt	$ 2,769		$ 2,030
Senior Notes \| 5.170% Senior Notes due 2027
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Stated interest rate	5.17%
Total debt	$ 399		399
Senior Notes \| 3.125% Senior Notes due 2031
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Stated interest rate	3.125%
Total debt	$ 497		496
Senior Notes \| 5.670% Senior Notes due 2032
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Stated interest rate	5.67%
Total debt	$ 348		348
Senior Notes \| 6.150% Senior Notes due 2037
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Stated interest rate	6.15%	6.15%
Total debt	$ 742		0
Senior Notes \| 4.000% Senior Notes due 2051
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Stated interest rate	4.00%
Total debt	$ 490		490
Surplus notes due 2027
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Total debt	250		250
FHLBI bank loans due 2034 & 2035
Schedule of Long Term and Short Term Debt Instruments [Line Items]
Total debt	$ 43		$ 47