<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.2.0.727</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>141</ContextCount>
  <ElementCount>217</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>48</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>101 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DocumentandEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>103 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfFinancialPositionUnclassified-InvestmentBasedOperations</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>104 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfFinancialPositionUnclassified-InvestmentBasedOperationsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>105 - Statement - Condensed Consolidated Statements of Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfIncomeInsuranceBasedRevenue</Role>
      <ShortName>Condensed Consolidated Statements of Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>106 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfOtherComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>107 - Statement - Condensed Consolidated Statement of Changes in Shareholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfShareholdersEquityAndOtherComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statement of Changes in Shareholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>108 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/StatementOfCashFlowsIndirectInvestmentBasedOperations</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>109 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsOrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>110 - Disclosure - Stock Options and Restricted Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsDisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock</Role>
      <ShortName>Stock Options and Restricted Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>111 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>112 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock</Role>
      <ShortName>Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>113 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsIncomeTaxDisclosureTextBlock</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>114 - Disclosure - Comprehensive Income and Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock</Role>
      <ShortName>Comprehensive Income and Accumulated Other Comprehensive Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>115 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsFairValueMeasurementInputsDisclosureTextBlock</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>116 - Disclosure - Treasury Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsTreasuryStockTextBlock</Role>
      <ShortName>Treasury Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>117 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsCommitmentsAndContingenciesDisclosureTextBlock</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>118 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsSubsequentEventsTextBlock</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>119 - Disclosure - Fair Value Measurements (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsFairValueMeasurementInputsDisclosureTextBlockPolicies</Role>
      <ShortName>Fair Value Measurements (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>120 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlockTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsEarningsPerShareTextBlock</ParentRole>
      <Position>19</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>121 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlockTables</Role>
      <ShortName>Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsInvestmentsInDebtAndMarketableEquitySecuritiesAndCertainTradingAssetsDisclosureTextBlock</ParentRole>
      <Position>20</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>122 - Disclosure - Comprehensive Income and Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlockTables</Role>
      <ShortName>Comprehensive Income and Accumulated Other Comprehensive Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsComprehensiveIncomeNoteTextBlock</ParentRole>
      <Position>21</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>123 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsFairValueMeasurementInputsDisclosureTextBlockTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://amerisafe.com/taxonomy/role/NotesToFinancialStatementsFairValueMeasurementInputsDisclosureTextBlock</ParentRole>
      <Position>22</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>124 - Disclosure - Basis of Presentation - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureBasisOfPresentationAdditionalInformation</Role>
      <ShortName>Basis of Presentation - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>125 - Disclosure - Stock Options and Restricted Stock - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureStockOptionsAndRestrictedStockAdditionalInformation</Role>
      <ShortName>Stock Options and Restricted Stock - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>126 - Disclosure - Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureEarningsPerShareCalculationOfBasicAndDilutedEarningsPerShare</Role>
      <ShortName>Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>127 - Disclosure - Investments - Gross Unrealized Gains and Losses and Amortized Cost and Fair Value of Investments Classified as Held-to-Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsGrossUnrealizedGainsAndLossesAndAmortizedCostAndFairValueOfInvestmentsClassifiedAsHeldtoMaturity</Role>
      <ShortName>Investments - Gross Unrealized Gains and Losses and Amortized Cost and Fair Value of Investments Classified as Held-to-Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>128 - Disclosure - Investments - Gross Unrealized Gains and Losses and Cost or Amortized Cost and Fair Value of Investments Classified as Available-for-Sale (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsGrossUnrealizedGainsAndLossesAndCostOrAmortizedCostAndFairValueOfInvestmentsClassifiedAsAvailableforSale</Role>
      <ShortName>Investments - Gross Unrealized Gains and Losses and Cost or Amortized Cost and Fair Value of Investments Classified as Available-for-Sale (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>129 - Disclosure - Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Held-to-Maturity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsSummaryOfAmortizedCostAndFairValueOfInvestmentsInFixedMaturitySecuritiesClassifiedAsHeldtoMaturity</Role>
      <ShortName>Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Held-to-Maturity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>130 - Disclosure - Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Available-for-Sale (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsSummaryOfAmortizedCostAndFairValueOfInvestmentsInFixedMaturitySecuritiesClassifiedAsAvailableforSale</Role>
      <ShortName>Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Available-for-Sale (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>131 - Disclosure - Investments - Investment Securities Continuous Unrealized Loss Position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsInvestmentSecuritiesContinuousUnrealizedLossPosition</Role>
      <ShortName>Investments - Investment Securities Continuous Unrealized Loss Position (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>132 - Disclosure - Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureInvestmentsAdditionalInformation</Role>
      <ShortName>Investments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>133 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureIncomeTaxesAdditionalInformation</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>134 - Disclosure - Comprehensive Income and Accumulated Other Comprehensive Income - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeAdditionalInformation</Role>
      <ShortName>Comprehensive Income and Accumulated Other Comprehensive Income - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>135 - Disclosure - Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Income (AOCI) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeScheduleOfChangesInAccumulatedOtherComprehensiveIncomeAOCI</Role>
      <ShortName>Comprehensive Income and Accumulated Other Comprehensive Income - Schedule of Changes in Accumulated Other Comprehensive Income (AOCI) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>136 - Disclosure - Comprehensive Income and Accumulated Other Comprehensive Income - Reclassification Out of Accumulated Other Comprehensive Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeReclassificationOutOfAccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Comprehensive Income and Accumulated Other Comprehensive Income - Reclassification Out of Accumulated Other Comprehensive Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>137 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasis</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>138 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities Measured at Amortized Cost (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfAssetsAndLiabilitiesMeasuredAtAmortizedCost</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets and Liabilities Measured at Amortized Cost (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>139 - Disclosure - Fair Value Measurements - Summary of Carrying Values and Corresponding Fair Values for Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfCarryingValuesAndCorrespondingFairValuesForFinancialInstruments</Role>
      <ShortName>Fair Value Measurements - Summary of Carrying Values and Corresponding Fair Values for Financial Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>140 - Disclosure - Fair Value Measurements - Summary of Changes in Fair Value of Assets Measured at Fair Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureFairValueMeasurementsSummaryOfChangesInFairValueOfAssetsMeasuredAtFairValue</Role>
      <ShortName>Fair Value Measurements - Summary of Changes in Fair Value of Assets Measured at Fair Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>141 - Disclosure - Treasury Stock - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureTreasuryStockAdditionalInformation</Role>
      <ShortName>Treasury Stock - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>142 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformation</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>143 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://amerisafe.com/taxonomy/role/DisclosureSubsequentEventsAdditionalInformation</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">In ''Condensed Consolidated Balance Sheets'', column(s) 2, 4, 5, 6 are contained in other reports, so were removed by flow through suppression.</Log>
    <Log type="Info">In ''Condensed Consolidated Statements of Cash Flows (Unaudited)'', column(s) 1, 2 are contained in other reports, so were removed by flow through suppression.</Log>
  </Logs>
  <InputFiles>
    <File>amsf-20150630.xml</File>
    <File>amsf-20150630_cal.xml</File>
    <File>amsf-20150630_def.xml</File>
    <File>amsf-20150630_lab.xml</File>
    <File>amsf-20150630_pre.xml</File>
    <File>amsf-20150630.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>

