XML 91 R80.htm IDEA: XBRL DOCUMENT v3.25.0.1

Loss and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 34,886	$ 41,396	$ 40,591
Minimum period of underwriting workers? compensation insurance from which historical loss data utilize	39 years

X

- Definition

Minimum period of underwriting workers compensation insurance from which historical loss data utilize.

+ References

No definition available.

+ Details

Name:	amsf_MinimumPeriodOfUnderwritingWorkersCompensationInsuranceFromWhichHistoricalLossDataUtilize
Namespace Prefix:	amsf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Unpaid Losses And Loss Expenses [Line Items]

+ References

No definition available.

+ Details

Name:	amsf_UnpaidLossesAndLossExpensesLineItems
Namespace Prefix:	amsf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-3

+ Details

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