Insurance Company Subsidiary Operations - Effects of Reinsurance on Premiums Written and Earned (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Written
Net premiums	$ 61.1	$ 38.3
Earned
Net premiums	27.7	26.4
WNFIC
Written
Direct premiums	886.5	740.9
Ceded premiums	886.5	740.9
Earned
Direct premiums	807.4	751.3
Ceded premiums	(807.4)	(751.3)
Quota Share Captive and Excess of Loss Layer Captive
Written
Assumed premiums	113.2	65.4
Net premiums	61.1	38.3
Earned
Assumed premiums	89.6	43.7
Net premiums	27.7	26.4
Quota Share Captive
Written
Ceded premiums	52.1	27.1
Net premiums	57.6
Earned
Ceded premiums	(61.9)	$ (17.3)
Net premiums	$ 24.2

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Amount of earned premiums ceded to other entities.

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Amount of written premiums ceded to other entities.

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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