Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Grouping, Financial Statement Captions
Carrying Value	$ 564.7	$ 575.2
HG Global Senior Notes
Balance Sheet Grouping, Financial Statement Captions
Fair Value	157.6	155.7
Carrying Value	146.8	146.5
Ark 2007 Subordinated Notes
Balance Sheet Grouping, Financial Statement Captions
Fair Value	29.1	28.4
Carrying Value	30.0	30.0
Ark 2021 Subordinated Notes
Balance Sheet Grouping, Financial Statement Captions
Fair Value	164.5	163.1
Carrying Value	154.6	153.7
Kudu Credit Facility
Balance Sheet Grouping, Financial Statement Captions
Fair Value	223.0	223.9
Carrying Value	203.7	208.3
Other Operations debt
Balance Sheet Grouping, Financial Statement Captions
Fair Value	31.1	38.2
Carrying Value	$ 29.6	$ 36.7