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Reinsurance - Additional Information (Details) - USD ($) | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Jun. 30, 2024 | Jun. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Reinsurance Retention Policy |  |  |  |  |  |
Ceded Premiums Earned | $ 81,939,000 | $ 85,692,000 |  |  | $ 262,785,000 | $ 275,400,000
Reinsurance Contract [Axis]: XOL Commutation |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Ceded Premiums Earned |  |  | $ 6,300,000 | $ 15,700,000 |  |
Catastrophe Excess of Loss |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Retension loss events | 100,000,000 |  |  |  | 100,000,000 |
Third event retention level | 3,750,000 |  |  |  | 3,750,000 |
First event retention level | 29,750,000 |  |  |  | 29,750,000 |
Second event retention level | 18,500,000 |  |  |  | $ 18,500,000 |
Quota Share Agreement | Shoreline Re |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Cession Rate |  |  |  |  | 45.00% |
Quota Share Agreement | Reinsurance Contract [Axis]: 06/01/2024 - 06/01/2026 | Shoreline Re |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Cession Rate |  |  |  |  | 30.00% |
Quota Share Agreement | Reinsurance Contract [Axis]: 06/01/2025 - 06/01/2026 | Shoreline Re |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Cession Rate |  |  |  |  | 45.00% |
American Coastal Insurance Company | Catastrophe Excess of Loss |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Insured long term debt project demand decrease |  |  |  |  | $ 69,000,000,000 |
Program provides sufficient coverage period |  |  |  |  | 1-in-100-year |
Percentage of singe occurrence exceeding protection purchased |  |  |  |  | 0.50% |
Program provides sufficient coverage return period |  |  |  |  | 1-in-203-year |
Reinsurance, excess retention, amount reinsured, per policy |  |  |  |  | $ 1,676,000,000 |
Event retention level | 14,000,000 |  |  |  | 14,000,000 |
Reinsurance, excess retention, amount reinsured, per event |  |  |  |  | $ 1,330,000,000 |
American Coastal Insurance Company | Catastrophe Excess of Loss | Maximum |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Program provides sufficient coverage probability rate |  |  |  |  | 0.10% |
American Coastal Insurance Company | All Other Perilds Catastrophe Excess of Loss |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Percentage of singe occurrence exceeding protection purchased |  |  |  |  | 0.20% |
Program provides sufficient coverage return period |  |  |  |  | 1-in-450-year |
Reinsurance, excess retention, amount reinsured, per policy |  |  |  |  | $ 176,400,000 |
Reinsurance, excess retention level per event | 88,200,000 |  |  |  | 88,200,000 |
American Coastal Insurance Company | Catastrophe Aggregate Excess of Loss |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
Reinsurance, excess retention, amount reinsured, per policy |  |  |  |  | 40,000,000 |
Event occurrence limit | 20,000,000 |  |  |  | 20,000,000 |
Reinsurance, aggregate retention |  |  |  |  | 40,000,000 |
UPC Re | Catastrophe Excess of Loss |  |  |  |  |  |
Reinsurance Retention Policy |  |  |  |  |  |
First event retention level | 15,750,000 |  |  |  | 15,750,000 |
Subsequent event retention level | $ 4,500,000 |  |  |  | $ 4,500,000 |

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