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Debt - Narrative (Details) € in Millions				1 Months Ended				3 Months Ended	6 Months Ended
Debt - Narrative (Details) € in Millions	Jul. 01, 2023	Apr. 29, 2022 USD ($)	Sep. 08, 2021 USD ($)	Sep. 30, 2021 USD ($)	Aug. 31, 2021	Jul. 31, 2021	Mar. 31, 2007 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2023 USD ($) credit_facility	Jun. 30, 2023 EUR (€) credit_facility	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jun. 16, 2022 USD ($)	Apr. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Aug. 11, 2021 USD ($)	Jul. 13, 2021 USD ($)	Jul. 13, 2021 EUR (€)
Debt Instrument
Debt									$ 566,100,000		$ 575,200,000
Debt covenant, maximum loan to value percent, period one									50.00%	50.00%
Debt covenant, maximum loan to value percent, period two									40.00%	40.00%
Debt covenant, maximum loan to value percent, period three									25.00%	25.00%
Debt covenant, maximum loan to value percent, period four									15.00%	15.00%
Debt covenant, maximum loan to value percent, period five									0.00%	0.00%
Debt covenant, maximum loan to value percent									27.90%	27.90%
Short-term investments \| Asset Pledged as Collateral
Debt Instrument
Investments pledged as collateral									$ 145,500,000		90,300,000
HG Global \| Interest Rate Cap
Debt Instrument
Notional amount													$ 150,000,000
Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Borrowings								$ 157,800,000
Unsecured Subordinated Debt \| Group Ark Insurance Limited \| Ark
Debt Instrument
Notes issued				$ 163,300,000				$ 163,300,000
Senior Notes \| Secured Debt
Debt Instrument
Borrowings		$ 150,000,000
Annual payments														$ 15,000,000
Interest reserve account									$ 29,700,000		$ 31,200,000		$ 29,200,000
Additional interest rate									1.00%
Senior Notes \| Secured Debt \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument
Basis spread on variable rate		6.30%
HG Senior Notes
Debt Instrument
Effective percentage									11.50%	11.50%	8.90%
HG Senior Notes \| Secured Debt
Debt Instrument
Outstanding balance									$ 150,000,000.0		$ 150,000,000.0
Debt									146,700,000		146,500,000
Ark 2007 Subordinated Notes, carrying value \| Ark Subordinated Debt
Debt Instrument
Outstanding balance									30,000,000.0		30,000,000.0
Ark 2007 Subordinated Notes, carrying value \| Junior Notes \| Ark
Debt Instrument
Face value							$ 30,000,000
Debt									30,000,000
Ark 2007 Subordinated Notes, carrying value \| Junior Notes \| USD-LIBOR \| Ark
Debt Instrument
Basis spread on variable rate							4.60%
Ark 2021 Subordinated Notes Tranche 1
Debt Instrument
Outstanding balance \| €										€ 39.1
Ark 2021 Subordinated Notes Tranche 1 \| Ark Subordinated Debt
Debt Instrument
Outstanding balance									42,600,000		41,300,000
Ark 2021 Subordinated Notes Tranche 1 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Notes issued																	$ 46,300,000	€ 39.1
Ark 2021 Subordinated Notes Tranche 1 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited \| EURIBOR
Debt Instrument
Basis spread on variable rate						5.75%
Ark 2021 Subordinated Notes Tranche 2 \| Ark Subordinated Debt
Debt Instrument
Outstanding balance									47,000,000		47,000,000.0
Ark 2021 Subordinated Notes Tranche 2 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Notes issued																$ 47,000,000
Ark 2021 Subordinated Notes Tranche 2 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited \| USD-LIBOR
Debt Instrument
Basis spread on variable rate					5.75%
Ark 2021 Subordinated Notes Tranche 3 \| Ark Subordinated Debt
Debt Instrument
Outstanding balance									70,000,000.0		70,000,000.0
Ark 2021 Subordinated Notes Tranche 3 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited
Debt Instrument
Additional interest rate			1.00%
Notes issued			$ 70,000,000
Solvency capital requirement				120.00%
Debt to capital requirement				40.00%
Ark 2021 Subordinated Notes Tranche 3 \| Unsecured Subordinated Debt \| Group Ark Insurance Limited \| USD-LIBOR
Debt Instrument
Basis spread on variable rate			6.10%
ING LOC Facility \| Secured Debt \| Ark \| Letter of Credit \| Uncollateralized
Debt Instrument
Total commitment under revolving credit facility															$ 50,000,000
Citibank LOC Facility \| Short-term investments \| Asset Pledged as Collateral
Debt Instrument
Investments pledged as collateral									107,400,000
Citibank LOC Facility \| Secured Debt
Debt Instrument
Line of credit									93,700,000
Citibank LOC Facility \| Secured Debt \| Ark \| Letter of Credit \| Collateral Pledged
Debt Instrument
Total commitment under revolving credit facility															$ 100,000,000
Lloyds LOC Facility \| Short-term investments \| Asset Pledged as Collateral
Debt Instrument
Investments pledged as collateral									38,100,000
Lloyds LOC Facility \| Secured Debt
Debt Instrument
Line of credit									35,000,000
Lloyds LOC Facility \| Secured Debt \| Ark \| Letter of Credit \| Collateral Pledged
Debt Instrument
Total commitment under revolving credit facility												$ 50,000,000
Kudu Bank Facility \| Asset Management (Kudu)
Debt Instrument
Total commitment under revolving credit facility									$ 300,000,000
Kudu Bank Facility \| Revolving Credit Facility
Debt Instrument
Effective percentage									0.25%	0.25%
Kudu Bank Facility \| Revolving Credit Facility \| Subsequent Event
Debt Instrument
Effective percentage	4.30%
Kudu Bank Facility \| Revolving Credit Facility \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Subsequent Event
Debt Instrument
Basis spread on variable rate	0.26%
Kudu Bank Facility \| Revolving Credit Facility \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Basis spread on variable rate									4.30%
Kudu Bank Facility \| Line of Credit \| Asset Management (Kudu)
Debt Instrument
Interest reserve									$ 13,400,000
Kudu Bank Facility \| Term Loan \| Asset Management (Kudu)
Debt Instrument
Percentage of borrowing base									35.00%	35.00%
Remaining borrowing capacity under revolving credit facility									$ 59,700,000
Other Operations \| Term Loan
Debt Instrument
Outstanding balance									$ 31,200,000		$ 37,400,000
Effective percentage									9.10%	9.10%	6.60%
Secured credit facilities \| credit_facility									4	4