Debt - Summary of Debt Outstanding (Details) € in Millions, $ in Millions	Sep. 30, 2025 USD ($)	Sep. 30, 2025 EUR (€)	Sep. 02, 2025 USD ($)	Jul. 21, 2025 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Debt Instrument
Total debt	$ 870.4					$ 562.5
Ark 2021 Subordinated Notes
Debt Instrument
Total debt	159.7					154.5
HG Global Senior Notes
Debt Instrument
Total debt	147.7					147.4
Kudu Credit Facility
Debt Instrument
Total debt	274.3					238.6
Bamboo Credit Facility
Debt Instrument
Total debt	104.6					0.0
Distinguished Credit Facility
Debt Instrument
Total debt	138.1					0.0
Distinguished other debt, carrying value
Debt Instrument
Total debt	10.6					0.0
Other Operations debt
Debt Instrument
Total debt	35.4					22.0
Subordinated Debt | Ark 2021 Subordinated Notes
Debt Instrument
Unamortized discount and issuance cost	(3.2)					(3.6)
Total debt	$ 159.7					$ 154.5
Effective Rate	10.20%	10.20%				11.80%
Subordinated Debt | Ark 2021 Subordinated Notes Tranche 1
Debt Instrument
Amount borrowed	$ 45.9	€ 39.1				$ 41.1
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
Senior Notes | HG Global Senior Notes
Debt Instrument
Amount borrowed	150.0					150.0
Unamortized discount and issuance cost	(2.3)					(2.6)
Total debt	$ 147.7					$ 147.4
Effective Rate	10.90%	10.90%				11.80%
Secured Debt | Kudu Credit Facility
Debt Instrument
Amount borrowed	$ 282.3				$ 253.3	$ 245.3	$ 225.3	$ 210.3	$ 210.3
Unamortized discount and issuance cost	(8.0)					(6.7)
Total debt	$ 274.3			$ 253.3		$ 238.6
Effective Rate	9.00%	9.00%				10.30%
Secured Debt | Bamboo Credit Facility
Debt Instrument
Amount borrowed	$ 109.5				$ 109.7	$ 0.0
Unamortized discount and issuance cost	(4.9)					0.0
Total debt	$ 104.6					0.0
Effective Rate	9.90%	9.90%
Secured Debt | Total Distinguished debt
Debt Instrument
Total debt	$ 148.7					0.0
Secured Debt | Distinguished Credit Facility
Debt Instrument
Amount borrowed	139.8		$ 90.2			0.0
Unamortized discount and issuance cost	(1.7)					0.0
Total debt	$ 138.1					0.0
Effective Rate	11.30%	11.30%
Secured Debt | Distinguished other debt, carrying value
Debt Instrument
Total debt	$ 10.6					0.0
Effective Rate	10.50%	10.50%
Secured Debt | Other Operations debt
Debt Instrument
Amount borrowed	$ 35.9					22.4
Unamortized discount and issuance cost	(0.5)					(0.4)
Total debt	$ 35.4					$ 22.0
Effective Rate	8.50%	8.50%				10.20%