Catastrophe Reinsurance - Catastrophe Reinsurance Premiums (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Liability for Catastrophe Claims [Line Items]
Ceded earned premiums	$ 33.1	$ 32.7	$ 42.7
Catastrophe Reinsurance
Liability for Catastrophe Claims [Line Items]
Ceded earned premiums	16.4	16.3	32.0
Operating Segments | Specialty Property & Casualty Insurance | Catastrophe Reinsurance
Liability for Catastrophe Claims [Line Items]
Ceded earned premiums	6.5	6.1	8.9
Operating Segments | Life Insurance | Catastrophe Reinsurance
Liability for Catastrophe Claims [Line Items]
Ceded earned premiums	0.3	0.7	0.6
Non-Core Operations | Catastrophe Reinsurance
Liability for Catastrophe Claims [Line Items]
Ceded earned premiums	$ 9.6	$ 9.5	$ 22.5