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Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Apr. 29, 1991 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2019 | Oct. 31, 2025 | Dec. 31, 2022 | Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Operating Lease, Liability |  | $ 9,854,000 | $ 21,543,000 |  |  |  |  |
Common Stock Voting Restrictions | 10.00% |  |  |  |  |  |  |
Common stock, par value (in dollars per share) |  |  |  |  |  |  |  | $ 0.01
Preferred stock, shares authorized |  | 20,000,000 | 20,000,000 |  |  |  |  |
Preferred Stock, Par or Stated Value Per Share |  | $ 0.01 |  |  |  |  |  | $ 0.01
Common stock, shares issued |  | 48,876,882 | 48,875,167 |  |  |  |  |
Common Stock Transfer Restrictions | 5.00% |  |  |  |  |  |  |
Common Stock Additional Transfer Restrictions |  |  |  |  | 5.00% |  |  |
Restricted Cash |  | $ 40,754,000 | $ 17,669,000 |  |  |  |  |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents |  | 70,090,000 | 47,275,000 | $ 19,223,000 |  |  | $ 19,940,000 |
Investment income due and accrued |  | $ 1,432,000 | $ 1,703,000 |  |  |  |  |
Accrued Investment Interest Receivable Write-off Period in Days |  | 90 |  |  |  |  |  |
Financial Assets Allowance for Credit Loss |  | $ 950,000 |  |  |  |  |  |
Preferred stock, shares outstanding (in shares) |  | 0 | 0 |  |  |  |  |
Short-Term Debt |  | $ 0 | $ 150,000,000 |  |  |  |  |
Debt Instrument, Convertible, Type of Equity Security |  | 3,500 |  |  |  |  |  |
Investment in less than 100 percent owned, Percentage |  | $ 0.74 |  |  |  |  |  |
Investments, Equity Interest Percent |  | 17.00% |  |  |  |  |  |
Long-term debt |  | $ 117,558,000 | 0 |  |  | $ 100,000,000 |  |
Adjustment of NCI to fair value |  |  | (10,276,000) |  |  |  |  |
Put / call option exercise |  | $ (1,815,000) |  |  |  |  |  |
Number of Put Options Exercised During Period |  | 0 |  |  |  |  |  |
Investment income due and accrued |  | $ 1,432,000 | 1,703,000 |  |  |  |  |
CECL Securities Factor for Consideration |  | 20.00% |  |  |  |  |  |
Medium-Term Note |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Long-term debt |  | $ 100,000,000 |  |  |  |  |  |
Revolving Credit Facility |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Short-Term Debt |  | $ 20,000,000 |  |  |  | $ 20,000,000 |  |
Specialty Property & Casualty Program |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Reinsurance, Reinsured Risk, Percentage |  | 70.00% |  |  |  |  |  |
Xchange |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 80.00% |  |  |  |  |  |
All Trans |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 85.00% |  |  |  |  |  |
Capacity Marine |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 80.00% |  |  |  |  |  |
Riverton |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 80.00% |  |  |  |  |  |
Pivix |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 74.00% |  |  |  |  |  |
Octave Ventures |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Ownership percentage |  | 60.00% |  |  |  |  |  |
Minimum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Useful Life in Years |  | 3 years |  |  |  |  |  |
Maximum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Useful Life in Years |  | 5 years |  |  |  |  |  |
Long-term Debt [Member] |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Interest Paid, Including Capitalized Interest, Operating and Investing Activities |  | $ 19,775,000 | $ 3,821,000 | $ 0 |  |  |  |

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