Debt - Debt Outstanding (Details) € in Millions, $ in Millions	Dec. 31, 2024 USD ($)	Dec. 31, 2024 EUR (€)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument
Amount borrowed	$ 575.8
Carrying Value	562.5		$ 564.6
HG Global Senior Notes
Debt Instrument
Carrying Value	147.4		146.9
Ark 2007 Subordinated Notes
Debt Instrument
Carrying Value	0.0		30.0
Ark 2021 Subordinated Notes
Debt Instrument
Carrying Value	154.5		155.5
Kudu Credit Facility
Debt Instrument
Carrying Value	238.6		203.8
Other Operations debt
Debt Instrument
Carrying Value	22.0		28.4
Senior Notes | HG Global Senior Notes
Debt Instrument
Amount borrowed	150.0		150.0
Unamortized discount and issuance cost	(2.6)		(3.1)
Carrying Value	$ 147.4		$ 146.9
Effective yield (as a percent)	11.80%	11.80%	11.90%
Subordinated Debt | Ark
Debt Instrument
Carrying Value	$ 154.5		$ 185.5
Effective yield (as a percent)	11.80%	11.80%	11.00%
Subordinated Debt | Ark 2007 Subordinated Notes
Debt Instrument
Amount borrowed	$ 0.0		$ 30.0
Subordinated Debt | Ark 2021 Subordinated Notes
Debt Instrument
Unamortized issuance cost	(3.6)		(4.2)
Carrying Value	154.5		155.5
Subordinated Debt | Ark 2021 Subordinated Notes, Tranche 1
Debt Instrument
Amount borrowed	41.1	€ 39.1	42.7
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	245.3		210.3
Unamortized issuance cost	(6.7)		(6.5)
Carrying Value	$ 245.3		$ 210.3	$ 215.2	$ 225.4
Effective yield (as a percent)	10.30%	10.30%	10.10%
Secured Debt | Other Operations debt
Debt Instrument
Amount borrowed	$ 22.4		$ 28.9
Unamortized issuance cost	$ (0.4)		$ (0.5)
Effective yield (as a percent)	10.20%	10.20%	10.20%