XML 64 R72.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Line of Credit - Additional Information (Detail) (USD $) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Oct. 31, 2007
Line of Credit Facility [Line Items] |  |  |
Maximum amount of line of credit |  |  | $ 20,000,000
Line of credit facility renewal period | 3 years |  |
Outstanding borrowings or letters of credit | 0 | 0 |
Line Of Credit Facility Expired December 2013 [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Payment on unused portion of the loan | 0.375% |  |
Total fee | 75,000 |  |
Line Of Credit Facility Expired December 2016 [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Payment on unused portion of the loan | 0.25% |  |
Total fee | $ 50,000 |  |

X
- Definition Line of credit facility renewal period. + References No definition available. + Details
Name: | amsf_LineOfCreditFacilityRenewalPeriod
Namespace Prefix: | amsf_
Data Type: | us-types:durationStringItemType
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