Insurance Company Subsidiary Operations - Effects of Reinsurance on Premiums Written and Earned (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Written
Net premiums	$ 79	$ 61
Earned
Net premiums	77	28
WNFIC
Written
Direct premiums	1,005	887
Ceded premiums	1,005	887
Earned
Direct premiums	946	807
Ceded premiums	946	807
Quota Share Captive and Excess of Loss Layer Captive
Written
Assumed premiums	153	113
Net premiums	79	61
Earned
Assumed premiums	151	90
Net premiums	77	28
Quota Share Captive
Written
Ceded premiums	74	52
Net premiums	75
Earned
Ceded premiums	74	$ 62
Net premiums	$ 73

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