Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 562.5	$ 564.6
Ark 2007 Subordinated Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0.0	30.5
Debt	0.0	30.0
Ark 2021 Subordinated Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	173.9	171.8
Debt	154.5	155.5
HG Global Senior Notes
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	157.2	158.7
Debt	147.4	146.9
Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	253.3	225.6
Debt	238.6	203.8
Other Operations debt
Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	23.1	30.0
Debt	$ 22.0	$ 28.4