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v3.24.0.1

Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Apr. 29, 1991 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2017 | Dec. 31, 2020 | Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Operating Lease, Liability |  | $ 22 | $ 25 |  |  |  |
Income Taxes Paid |  | $ 11 | $ 6 | $ 15 |  |  |
Common Stock Voting Restrictions | 10.00% |  |  |  |  |  |
Common Stock, Par or Stated Value 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 |  | 46,659,144 | 46,658,990 |  |  |  |
Warrant Exercised During Period Shares |  | 1,503 | 0 | 132 |  |  |
Common Stock Transfer Restrictions | 5.00% |  |  |  |  |  |
Common Stock Additional Transfer Restrictions |  |  |  |  | 5.00% |  |
Restricted Cash |  | $ 12 | $ 14 | $ 5 |  |  |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents |  | 274 | 61 | 23 |  | $ 35 |
Investment income due and accrued |  | $ 14 | $ 10 |  |  |  |
Accrued Investment Interest Receivable Write-off Period in Days |  | 90 |  |  |  |  |
Weighted average period of future premiums |  | 7 years 8 months 12 days | 8 years |  |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate |  | 3.20% | 3.00% |  |  |  |
Investment income due and accrued |  | $ 14 | $ 10 |  |  |  |
CECL Securities Factor for Consideration |  | 20.00% |  |  |  |  |
Specialty Property & Casualty Program |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Reinsurance, Reinsured Risk, Percentage |  | 70.00% |  |  |  |  |
Xchange |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  | 80.00% |  |  |  |  |
All Trans |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  | 85.00% |  |  |  |  |
Capacity Marine |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  | 80.00% |  |  |  |  |
Riverton |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  | 80.00% |  |  |  |  |
Minimum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 3 years |  |  |  |  |
Maximum [Member] | Furniture and Fixtures [Member] |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  | 5 years |  |  |  |  |
Long-term Debt [Member] |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Interest Paid, Including Capitalized Interest, Operating and Investing Activities |  | $ 50 | 283 | 80 |  |  |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |
Restricted Cash |  | $ 246 | $ 17 | $ 2 |  |  |
Estimated Future Premium Payments Weighted Average Discounted Rate |  | 6.30% | 6.80% |  |  |  |

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