XML 43 R73.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Line of Credit - Additional Information (Detail) (USD $) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Oct. 31, 2007 | Dec. 31, 2013 | Dec. 31, 2010 | Dec. 31, 2014
Line of Credit Facility [Line Items] |  |  |  |
Maximum amount of line of credit | $ 20,000,000 us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity |  |  |
Line of credit facility renewal period | 3 years | 3 years | 3 years |
Outstanding borrowings or letters of credit |  | 0 us-gaap_LettersOfCreditOutstandingAmount |  |
Line of Credit Facility Expired December 2016 [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Payment on unused portion of the loan |  |  |  | 0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage / us-gaap_CreditFacilityAxis = amsf_LineOfCreditFacilityExpiredDecemberTwoThousandSixteenMember
Total fee |  |  |  | $ 50,000 us-gaap_LineOfCreditFacilityCommitmentFeeAmount / us-gaap_CreditFacilityAxis = amsf_LineOfCreditFacilityExpiredDecemberTwoThousandSixteenMember

X
- Definition Line of credit facility renewal periods. + References No definition available. + Details
Name: | amsf_LineOfCreditFacilityRenewalPeriods
Namespace Prefix: | amsf_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of the fee for available but unused credit capacity under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
Name: | us-gaap_LineOfCreditFacilityCommitmentFeeAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 22 -Article 5 + Details
Name: | us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
Name: | us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_CreditFacilityAxis=amsf_LineOfCreditFacilityExpiredDecemberTwoThousandSixteenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |