Event Retention Level

No definition available.

Name:	acic_EventRetentionLevel
Namespace Prefix:	acic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	dei_DocumentPeriodEndDate
Namespace Prefix:	dei_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of earned premiums ceded to other entities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-17(Column C))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477965/944-235-S99-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479032/944-605-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478832/944-605-45-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479032/944-605-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479032/944-605-50-1

+ Details

Name:	us-gaap_CededPremiumsEarned
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-3

+ Details

Name:	us-gaap_ReinsuranceRetentionExcessRetentionAmountReinsuredPerEvent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_ReinsuranceRetentionExcessRetentionAmountReinsuredPerPolicy
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ References

+ Details

Name:	us-gaap_ReinsuranceRetentionPolicyLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	acic_SubsidiaryAxis=acic_InterboroInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	acic_CatastropheReinsuranceContractAxis=acic_CatastropheExcessOfLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	acic_SubsidiaryAxis=acic_AmericanCoastalInsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	acic_CatastropheReinsuranceContractAxis=acic_AllOtherPerildsCatastropheExcessOfLossMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	acic_SubsidiaryAxis=acic_UPCReMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ReinsuranceContractAxis=XOL Commutation
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended
Reinsurance (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Reinsurance Retention Policy
Document Period End Date	Mar. 31, 2024
Ceded Premiums Earned	$ 100,092		$ 57,152
Interboro Insurance \| Catastrophe Excess of Loss
Reinsurance Retention Policy
Reinsurance, Excess Retention, Amount Reinsured, Per Policy	82,000
Event Retention Level	3,000
American Coastal Insurance Company \| Catastrophe Excess of Loss
Reinsurance Retention Policy
Reinsurance, Excess Retention, Amount Reinsured, Per Policy	1,300,000
Event Retention Level	10,000
Reinsurance, Excess Retention, Amount Reinsured, Per Event	1,100,000
American Coastal Insurance Company \| All Other Perilds Catastrophe Excess of Loss
Reinsurance Retention Policy
Reinsurance, Excess Retention, Amount Reinsured, Per Policy	172,000
UPC Re \| Catastrophe Excess of Loss
Reinsurance Retention Policy
Event Retention Level	2,250
Reinsurance Contract [Axis]: XOL Commutation
Reinsurance Retention Policy
Ceded Premiums Earned	$ 9,400	$ 6,300