XML 81 R70.htm IDEA: XBRL DOCUMENT v3.25.0.1

Reinsurance - Schedule of Unsecured Reinsurance Recoverables from Reinsurers (Detail) - USD ($) $ in Thousands		Dec. 31, 2024	Dec. 31, 2023
Ceded Credit Risk [Line Items]
Total reinsurance recoverables		$ 117,019	$ 129,963
Allowance for credit losses		(300)	$ (360)
Funds withheld and letters of credit related to the above recoverables		(69,556)
Total unsecured amounts recoverable from reinsurers		47,463
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk
Ceded Credit Risk [Line Items]
Total reinsurance recoverables		117,019
Total amounts recoverable from reinsurers		117,319
Allowance for credit losses		(300)
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Hannover Reinsurance (Ireland) Limited [Member] | A.M. Best Rating, A+ [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	[1]	51,330
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Arch Reinsurance Company | A.M. Best Rating, A+ [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	[1]	25,502
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Minnesota Workers' Compensation Reinsurance Association [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	[1]	8,576
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Munich Reinsurance America, Inc [Member] | A.M. Best Rating, A+ [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	[1]	8,512
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Allianz Risk Transfer AG (Bermuda) [Member] | A.M. Best Rating, A+ [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables		5,963
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Odyssey America Reinsurance Corporation [Member] | A.M. Best Rating, A+ [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables		4,048
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk | Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables		$ 13,388
[1] Current participant in our 2025 reinsurance program.

X

- Definition

Letters of credit from the reinsurer and Amount of the reinsurer's funds held on its behalf by the ceding insurer, including funds held in trust, under reinsurance treaties or contracts with the assuming insurer as security for the payment of the obligations there under.

+ References

No definition available.

+ Details

Name:	amsf_FundsHeldAndLettersOfCredit
Namespace Prefix:	amsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Unsecured amounts recoverables from reinsurance net.

+ References

No definition available.

+ Details

Name:	amsf_UnsecuredAmountsRecoverablesFromReinsuranceNet
Namespace Prefix:	amsf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477351/944-825-50-1B

+ Details

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

X

- Definition

Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477409/944-310-45-5

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_ReinsuranceRecoverables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of allowance for credit loss on reinsurance recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477409/944-310-45-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_ReinsuranceRecoverablesAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477409/944-310-45-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

+ Details

Name:	us-gaap_ReinsuranceRecoverablesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=us-gaap_ReinsuranceRecoverableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_ReinsurerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_HannoverReinsuranceIrelandLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingAMBestAxis=srt_AMBestAPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_ArchReinsuranceCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_MinnesotaWorkersCompensationReinsuranceAssociationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_MunichReinsuranceAmericaIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_AllianzRiskTransferAGBermudaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_OdysseyAmericaReinsuranceCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_CededCreditRiskAxis=amsf_OtherReinsurersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: