v3.26.3
Basis of Presentation - Additional Information (Detail)
9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Percentage of comparable consolidated amounts
95.00%
95.00%
X
- Definition
Percentage of comparable consolidated amount.
+ References
No definition available.
+ Details
Name:
amsf_PercentageOfComparableConsolidatedAmount
Namespace Prefix:
amsf_
Data Type:
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Balance Type:
na
Period Type:
duration
X
- References
No definition available.
+ Details
Name:
us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix:
us-gaap_
Data Type:
xbrli:stringItemType
Balance Type:
na
Period Type:
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