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Financial Guarantee Insurance Contracts - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Dec. 31, 2024 | Sep. 30, 2024 | Jun. 30, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Sep. 30, 2023 | Jun. 30, 2023 | Mar. 31, 2023 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ceded Loss And Loss Expenses Paid Not Yet Recovered |  |  |  |  | $ 8,765 |  |  |  |  | $ 8,765 | $ 1,397 |
Reinsurance Payable | $ 53,002 |  |  |  | 29,666 |  |  |  | $ 53,002 | 29,666 |  |
Reinsurance recoveries of losses included in losses and loss expenses |  |  |  |  |  |  |  |  | (191,151) | (113,622) | (52,960) |
Amortization of intangible assets | 8,901 | $ 6,423 | $ 1,139 | $ 1,139 | 1,139 | $ 1,079 | $ 966 | $ 967 | 17,602 | 4,152 | 2,921 |
Intangible Assets, Gross (Excluding Goodwill) | 371,680 |  |  |  | 71,108 |  |  |  | 371,680 | 71,108 |  |
Finite-Lived Intangible Assets, Accumulated Amortization | 26,905 |  |  |  | 9,705 |  |  |  | 26,905 | 9,705 |  |
Intangible assets, less accumulated amortization | 344,775 |  |  |  | 61,403 |  |  |  | 344,775 | 61,403 |  |
Allowance for Doubtful Accounts, Premiums and Other Receivables | 142 |  |  |  | 69 |  |  |  | 142 | 69 | 0 | $ 0
Premium Receivable, Credit Loss Expense (Reversal) |  |  |  |  |  |  |  |  | 73 | 69 | 0 |
Premium Receivable, Allowance for Credit Loss, Writeoff |  |  |  |  |  |  |  |  | 0 | 0 | 0 |
Reinsurance Recoverable, Allowance for Credit Loss | 100 |  |  |  | 100 |  |  |  | 100 | 100 |  |
Reinsurance Recoverables, Gross | 306,290 |  |  |  |  |  |  |  | 306,290 |  |  |
Net unsecured reinsurance recoverable | 232,310 |  |  |  |  |  |  |  | 232,310 |  |  |
Reinsurance Recoverable, Gross, All Other | 94,726 |  |  |  |  |  |  |  | 94,726 |  |  |
Unsecured Reinsurance Recoverable, All Other | 44,329 |  |  |  |  |  |  |  | 44,329 |  |  |
Uncollateralized Credit Exposure Supoorted by Unlimited Uncapped Indemnity | 35,146 |  |  |  | $ 43,688 |  |  |  | 35,146 | 43,688 |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years |  |  |  |  |  |  |  |  | 18,231 | $ 1,878 | $ 0 |
Financial Guarantee |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ceded Loss And Loss Expenses Paid Not Yet Recovered | 36,210 |  |  |  |  |  |  |  | 36,210 |  |  |
Financial Guarantee | Assured Guaranty Re Ltd [Member] |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 20,052 |  |  |  |  |  |  |  | 20,052 |  |  |
Net unsecured reinsurance recoverable | 16,653 |  |  |  |  |  |  |  | 16,653 |  |  |
Property and Casualty, Commercial Insurance | QBE Insurance Corporation |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 31,502 |  |  |  |  |  |  |  | 31,502 |  |  |
Net unsecured reinsurance recoverable | 31,502 |  |  |  |  |  |  |  | 31,502 |  |  |
Property and Casualty, Commercial Insurance | General Reinsurance Company |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance Recoverables, Gross | 135,706 |  |  |  |  |  |  |  | 135,706 |  |  |
Net unsecured reinsurance recoverable | $ 117,537 |  |  |  |  |  |  |  | $ 117,537 |  |  |
Maximum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |  |  |  |  |  |
Insurance [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Useful Life - Years | 5 years |  |  |  |  |  |  |  | 5 years |  |  |

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