Debt - Narrative (Details) € in Millions				1 Months Ended				3 Months Ended			6 Months Ended
	Jul. 01, 2023	Apr. 29, 2022 USD ($)	Sep. 08, 2021 USD ($)	Sep. 30, 2021 USD ($)	Aug. 31, 2021	Jul. 31, 2021	Mar. 31, 2007 USD ($)	Mar. 31, 2024 USD ($) credit_facility	Mar. 31, 2023 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023	Mar. 31, 2024 EUR (€) credit_facility	Sep. 30, 2022 USD ($)	Jun. 16, 2022 USD ($)	Apr. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) letterOfCredit	Aug. 11, 2021 USD ($)	Jul. 13, 2021 USD ($)	Jul. 13, 2021 EUR (€)
Debt Instrument
Repayments of notes								$ 32,600,000	$ 20,000,000.0
Interest Rate Cap | Subsidiary - HG Global
Debt Instrument
Notional amount															$ 150,000,000
Ark 2007 Subordinated Notes | Junior Subordinated Debt
Debt Instrument
Face value							$ 30,000,000
Repayments of notes								30,000,000
Ark 2007 Subordinated Notes | Junior Subordinated Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate							4.60%
Ark 2021 Subordinated Notes | Subordinated Debt
Debt Instrument
Face value				$ 163,300,000						$ 163,300,000
Proceeds from debt, net of debt issuance costs										$ 157,800,000
Ark 2021 Subordinated Notes Tranche 1 | Subordinated Debt
Debt Instrument
Face value																			$ 46,300,000	€ 39.1
Outstanding balance								42,400,000			$ 42,700,000		€ 39.1
Ark 2021 Subordinated Notes Tranche 1 | Subordinated Debt | Euro Interbank Offered Rate (EURIBOR)
Debt Instrument
Basis spread on variable rate						5.75%
Ark 2021 Subordinated Notes Tranche 2 | Subordinated Debt
Debt Instrument
Face value																		$ 47,000,000
Outstanding balance								$ 47,000,000.0			47,000,000.0
Ark 2021 Subordinated Notes Tranche 2 | Subordinated Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate					5.75%
Ark 2021 Subordinated Notes Tranche 3 | Subordinated Debt
Debt Instrument
Face value			$ 70,000,000
Additional interest rate								1.00%
Debt instrument, period for interest rate increase			10 years
Solvency capital requirement				120.00%
Debt to capital requirement				40.00%
Outstanding balance								$ 70,000,000.0			70,000,000.0
Ark 2021 Subordinated Notes Tranche 3 | Subordinated Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate			6.10%
ING LOC Facility | Line of Credit | Letter of Credit
Debt Instrument
Number of letter of credit agreements | letterOfCredit																	2
Total commitment under revolving credit facility																	$ 50,000,000
Citibank LOC Facility | Line of Credit | Letter of Credit
Debt Instrument
Total commitment under revolving credit facility																	$ 125,000,000
Letters of credit outstanding								111,500,000
Pledged collateral								136,900,000
Lloyds LOC Facility | Line of Credit | Letter of Credit
Debt Instrument
Total commitment under revolving credit facility														$ 100,000,000
Letters of credit outstanding								35,400,000
Pledged collateral								$ 65,000,000
HG Global Senior Notes | Senior Notes
Debt Instrument
Face value		$ 150,000,000
Additional interest rate								1.00%
Outstanding balance								$ 150,000,000			150,000,000.0
Stated margin		6.00%
Anniversary of funding date		5 years
Annual payments																$ 15,000,000
Interest accrued multiplier															8
Interest reserve account, maximum															$ 29,300,000
Interest reserve account								30,500,000			30,400,000
HG Global Senior Notes | Senior Notes | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument
Basis spread on variable rate		0.26%
Kudu Credit Facility | Secured Debt
Debt Instrument
Face value								300,000,000
Repayments of notes								0	$ 16,900,000
Outstanding balance								210,300,000			210,300,000
Stated margin	4.30%											4.30%
Restricted cash								$ 15,100,000			$ 14,900,000
Debt covenant, maximum loan to value percent								23.10%					23.10%
Percentage of borrowing base								35.00%					35.00%
Kudu Credit Facility | Secured Debt | Debt Covenant, Period 1
Debt Instrument
Debt covenant, loan to value percent								50.00%					50.00%
Kudu Credit Facility | Secured Debt | Debt Covenant, Period 2
Debt Instrument
Debt covenant, loan to value percent								40.00%					40.00%
Kudu Credit Facility | Secured Debt | Debt Covenant, Period 3
Debt Instrument
Debt covenant, loan to value percent								25.00%					25.00%
Kudu Credit Facility | Secured Debt | Debt Covenant, Period 4
Debt Instrument
Debt covenant, loan to value percent								15.00%					15.00%
Kudu Credit Facility | Secured Debt | Debt Covenant, Period 5
Debt Instrument
Debt covenant, loan to value percent								0.00%					0.00%
Kudu Credit Facility | Secured Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate												0.25%
Kudu Credit Facility | Secured Debt | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument
Basis spread on variable rate	0.26%										0.26%
Other Operations debt | Secured Debt
Debt Instrument
Outstanding balance								$ 26,400,000			$ 28,900,000
Secured credit facilities | credit_facility								4					4