Catastrophe Reinsurance - Catastrophe Losses and LAE (Details) - Catastrophe - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	$ 87.6	$ 75.2	$ 102.4
Specialty Property & Casualty Insurance
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	32.2	23.6	16.0
Non-Core Operations
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	52.4	48.3	73.5
Life Insurance
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	$ 3.0	$ 3.3	$ 12.9