Debt - Summary of Debt Outstanding (Details) € in Millions, $ in Millions	Sep. 30, 2023 USD ($)	Sep. 30, 2023 EUR (€)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument
Total debt	$ 564.7			$ 575.2
HG Global Senior Notes
Debt Instrument
Total debt	146.8			146.5
Ark 2007 Subordinated Notes
Debt Instrument
Total debt	30.0			30.0
Ark 2021 Subordinated Notes
Debt Instrument
Total debt	154.6			153.7
Kudu Credit Facility
Debt Instrument
Total debt	203.7			208.3
Other Operations debt
Debt Instrument
Total debt	29.6			36.7
Senior Notes | HG Global Senior Notes
Debt Instrument
Amount borrowed	150.0			150.0
Unamortized discount and issuance cost	(3.2)			(3.5)
Total debt	$ 146.8			$ 146.5
Effective Rate	11.80%	11.80%		8.90%
Subordinated Debt | Ark
Debt Instrument
Total debt	$ 184.6			$ 183.7
Effective Rate	10.80%	10.80%		7.60%
Subordinated Debt | Ark 2007 Subordinated Notes
Debt Instrument
Amount borrowed	$ 30.0			$ 30.0
Subordinated Debt | Ark 2021 Subordinated Notes
Debt Instrument
Unamortized issuance cost	(4.3)			(4.6)
Total debt	154.6			153.7
Subordinated Debt | Ark 2021 Subordinated Notes Tranche 1
Debt Instrument
Amount borrowed	41.9	€ 39.1		41.3
Subordinated Debt | Ark 2021 Subordinated Notes Tranche 2
Debt Instrument
Amount borrowed	47.0			47.0
Subordinated Debt | Ark 2021 Subordinated Notes Tranche 3
Debt Instrument
Amount borrowed	70.0			70.0
Secured Debt | Kudu Credit Facility
Debt Instrument
Amount borrowed	210.3			215.2
Unamortized issuance cost	(6.6)			(6.9)
Total debt	$ 210.3		$ 210.3	$ 215.2	$ 260.4	$ 260.4	$ 225.4
Effective Rate	9.90%	9.90%		6.10%
Secured Debt | Other Operations debt
Debt Instrument
Amount borrowed	$ 30.1			$ 37.4
Unamortized issuance cost	$ (0.5)			$ (0.7)
Effective Rate	10.30%	10.30%		6.60%