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Retension loss events.

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Subsequent Event Retention Level

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Third Event Retention Level

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For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

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Amount of earned premiums ceded to other entities.

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Amount per event of risk ceded to reinsurer in excess of risk undertaken originally by insurer that is not ceded to reinsurer.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reinsurance - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reinsurance Retention Policy
Document Period End Date			Jun. 30, 2025
Ceded Premiums Earned	$ 87,017,000	$ 92,069,000	$ 180,846,000	$ 189,708,000
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			$ 60,000,000,000
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-201-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