XML 113 R97.htm IDEA: XBRL DOCUMENT
v3.22.4

Concentration of Operations - Net Premiums Earned for the Top Ten States (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 271,698 | $ 275,993 | $ 304,427
Premium earned percentage | 100.00% | 100.00% | 100.00%
Florida [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 31,955 | $ 31,514 | $ 34,617
Premium earned percentage | 11.80% | 11.40% | 11.40%
Georgia [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 30,831 | $ 34,772 | $ 37,926
Premium earned percentage | 11.30% | 12.60% | 12.50%
Pennsylvania [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 21,017 | $ 19,574 | $ 24,340
Premium earned percentage | 7.70% | 7.10% | 8.00%
Louisiana [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 21,804 | $ 20,476 | $ 22,668
Premium earned percentage | 8.00% | 7.40% | 7.40%
North Carolina [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 17,883 | $ 15,964 | $ 17,338
Premium earned percentage | 6.60% | 5.80% | 5.70%
Illinois [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 12,209 | $ 13,680 | $ 14,802
Premium earned percentage | 4.50% | 5.00% | 4.90%
Virginia [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 11,537 | $ 12,579 | $ 14,041
Premium earned percentage | 4.30% | 4.60% | 4.60%
Minnesota [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 9,827 | $ 10,612 | $ 11,057
Premium earned percentage | 3.60% | 3.80% | 3.60%
Wisconsin [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 12,007 | $ 13,108 | $ 12,263
Premium earned percentage | 4.40% | 4.70% | 4.00%
South Carolina [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 9,808 | $ 9,186 | $ 11,270
Premium earned percentage | 3.60% | 3.30% | 3.70%
All Others [Member] |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |
Net premiums earned | $ 92,820 | $ 94,528 | $ 104,105
Premium earned percentage | 34.20% | 34.30% | 34.20%

X
- Definition Premiums earned percentage. + References No definition available. + Details
Name: | amsf_PremiumsEarnedPercentage
Namespace Prefix: | amsf_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule Of Premiums Earned Net By Segment [Line Items] + References No definition available. + Details
Name: | amsf_ScheduleOfPremiumsEarnedNetBySegmentLineItems
Namespace Prefix: | amsf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column E)) -URI https://asc.fasb.org/extlink&oid=120401096&loc=d3e574992-122915 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(c)) -URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI https://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_PremiumsEarnedNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_FL
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_GA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_PA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_LA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_NC
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_IL
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_VA
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_MN
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_WI
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=stpr_SC
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=amsf_AllOtherStatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |