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Short-Term and Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Short-term debt		$ 0	$ 24
Total short-term debt		0	24
Total long-term debt		1,426	2,173
Repayment of debt		225	50	$ 0
6.03% surplus note, due 2028 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 750	750
Stated interest rate		6.03%
6.56% surplus note, due 2028 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 500	500
Stated interest rate		6.56%
SOFR + 111 bps surplus note, due 2028 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 0	$ 71
Variable rate			1.11%
Repayment of debt	$ 71
SOFR + 226 bps surplus note, due 2028 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		0	$ 522
Variable rate			2.26%
SOFR + 200 bps surplus note, due 2035 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 30	$ 30
Variable rate		2.00%
SOFR + 155 bps surplus note, due 2037 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 25	25
Variable rate		1.55%
4.20% surplus note, due 2037 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 50	50
Stated interest rate		4.20%
SOFR + 100 bps surplus note, due 2037 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 0	$ 154
Variable rate			1.00%
Repayment of debt	$ 154
4.225% surplus note, due 2037 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 28	$ 28
Stated interest rate		4.225%
4.00% surplus note, due 2037 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 30	30
Stated interest rate		4.00%
4.50% surplus note, due 2038 \| Subordinated Debt
Debt Instrument [Line Items]
Surplus notes		$ 13	$ 13
Stated interest rate		4.50%