XML 126 R92.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Concentration of Operations (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Net Premiums earned for different lines of business |  |  |  |  |  |  |  |  |  |  |
Premiums earned | $ 78,741 | $ 72,425 | $ 69,733 | $ 69,790 | $ 66,211 | $ 64,454 | $ 60,261 | $ 60,089 | $ 290,689 | $ 251,015 | $ 218,881
Premium earned percentage |  |  |  |  |  |  |  |  | 100.00% | 100.00% | 100.00%
Workers compensation [Member] |  |  |  |  |  |  |  |  |  |  |
Net Premiums earned for different lines of business |  |  |  |  |  |  |  |  |  |  |
Premiums earned |  |  |  |  |  |  |  |  | 290,538 | 249,966 | 217,810
Premium earned percentage |  |  |  |  |  |  |  |  | 99.90% | 99.60% | 99.50%
General Liability [Member] |  |  |  |  |  |  |  |  |  |  |
Net Premiums earned for different lines of business |  |  |  |  |  |  |  |  |  |  |
Premiums earned |  |  |  |  |  |  |  |  | $ 151 | $ 1,049 | $ 1,071
Premium earned percentage |  |  |  |  |  |  |  |  | 0.10% | 0.40% | 0.50%

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

X
- Definition Premiums earned on the income statement for all insurance and reinsurance contracts after subtracting any amounts ceded to another insurer and adding premiums assumed from other insurers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(c)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 113 -Paragraph 27 -Subparagraph a, b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
Name: | us-gaap_PremiumsEarnedNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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