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Debt - Narrative (Details) € in Millions |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended |  |  |  |  |  |  |  |
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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 |  |  |  |  |  |  |  |

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