<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>87</ContextCount>
  <ElementCount>202</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>30</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>75000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>75010 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_StatementCONDENSEDCONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>75020 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_StatementCONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>75030 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_StatementCONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>75040 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/StatementCondensedConsolidatedStatementsOfComprehensiveLoss</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>75050 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/StatementCondensedConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>75070 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995455 - Disclosure - Nature of the Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureNatureOfBusiness</Role>
      <ShortName>Nature of the Business</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Marketable Securities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureMarketableSecurities</Role>
      <ShortName>Marketable Securities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995505 - Disclosure - Accrued Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureAccruedExpenses</Role>
      <ShortName>Accrued Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995525 - Disclosure - Stock Option and Grant Plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlan</Role>
      <ShortName>Stock Option and Grant Plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995535 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureStockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Net Loss Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureNetLossPerShare</Role>
      <ShortName>Net Loss Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Asset Acquisitions and Collaboration Agreements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureAssetAcquisitionsAndCollaborationAgreements</Role>
      <ShortName>Asset Acquisitions and Collaboration Agreements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegments</Role>
      <ShortName>Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Marketable Securities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureMarketableSecuritiesTables</Role>
      <ShortName>Marketable Securities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/DisclosureMarketableSecurities</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Accrued Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureAccruedExpensesTables</Role>
      <ShortName>Accrued Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureAccruedExpenses</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995645 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurements</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995655 - Disclosure - Stock Option and Grant Plan (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlanTables</Role>
      <ShortName>Stock Option and Grant Plan (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlan</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995665 - Disclosure - Net Loss Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureNetLossPerShareTables</Role>
      <ShortName>Net Loss Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/DisclosureNetLossPerShare</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegmentsTables</Role>
      <ShortName>Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegments</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995695 - Disclosure - Marketable Securities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureMarketableSecuritiesAdditionalInformationDetails</Role>
      <ShortName>Marketable Securities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995705 - Disclosure - Marketable Securities - Schedule of Marketable Securities Classified as Available-for-sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureMarketableSecuritiesScheduleOfMarketableSecuritiesClassifiedAsAvailableforsaleDetails</Role>
      <ShortName>Marketable Securities - Schedule of Marketable Securities Classified as Available-for-sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995745 - Disclosure - Accrued Expenses - Schedule of Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureAccruedExpensesScheduleOfAccruedExpensesDetails</Role>
      <ShortName>Accrued Expenses - Schedule of Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureFairValueMeasurementsScheduleOfFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995765 - Disclosure - Stock Option and Grant Plan - Summary of Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlanSummaryOfStockOptionActivityDetails</Role>
      <ShortName>Stock Option and Grant Plan - Summary of Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Stock Option and Grant Plan - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlanAdditionalInformationDetails</Role>
      <ShortName>Stock Option and Grant Plan - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995785 - Disclosure - Stock Option and Grant Plan - Summary of Restricted Stock Unit Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlanSummaryOfRestrictedStockUnitActivityDetails</Role>
      <ShortName>Stock Option and Grant Plan - Summary of Restricted Stock Unit Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995795 - Disclosure - Stock Option and Grant Plan - Summary of Performance-Based Restricted Stock Unit Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureStockOptionAndGrantPlanSummaryOfPerformancebasedRestrictedStockUnitActivityDetails</Role>
      <ShortName>Stock Option and Grant Plan - Summary of Performance-Based Restricted Stock Unit Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Stock Option and Grant Plan - Summary of Stock-Based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureStockOptionAndGrantPlanSummaryOfStockbasedCompensationExpenseDetails</Role>
      <ShortName>Stock Option and Grant Plan - Summary of Stock-Based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Stock Option and Grant Plan - Summary of Unrecognized Stock-Based Compensation Expense and Weighted-Average Recognition Period (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/Role_DisclosureStockOptionAndGrantPlanSummaryOfUnrecognizedStockBasedCompensationExpenseAndWeightedAverageRecognitionPeriodDetails</Role>
      <ShortName>Stock Option and Grant Plan - Summary of Unrecognized Stock-Based Compensation Expense and Weighted-Average Recognition Period (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Stockholders' Equity - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureStockholdersEquityAdditionalInformationDetails</Role>
      <ShortName>Stockholders' Equity - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995835 - Disclosure - Net Loss Per Share - Schedule of Antidilutive Shares Excluded from the Calculation of Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureNetLossPerShareScheduleOfAntidilutiveSharesExcludedFromTheCalculationOfDilutedNetLossPerShareDetails</Role>
      <ShortName>Net Loss Per Share - Schedule of Antidilutive Shares Excluded from the Calculation of Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995845 - Disclosure - Commitments and Contingencies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetails</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995855 - Disclosure - Asset Acquisitions and Collaboration Agreements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureAssetAcquisitionsAndCollaborationAgreementsAdditionalInformationDetails</Role>
      <ShortName>Asset Acquisitions and Collaboration Agreements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995865 - Disclosure - Segments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegmentsAdditionalInformationDetails</Role>
      <ShortName>Segments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995875 - Disclosure - Segments - Schedule of Segment Revenue and Expenses to Consolidated Net Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegmentsScheduleOfSegmentRevenueAndExpensesToConsolidatedNetLossDetails</Role>
      <ShortName>Segments - Schedule of Segment Revenue and Expenses to Consolidated Net Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995885 - Disclosure - Segments - Schedule of Segment Revenue and Expenses to Consolidated Net Loss (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSegmentsScheduleOfSegmentRevenueAndExpensesToConsolidatedNetLossParentheticalDetails</Role>
      <ShortName>Segments - Schedule of Segment Revenue and Expenses to Consolidated Net Loss (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="amlx-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995895 - Disclosure - Subsequent Events - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.amylyx.com/20260331/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails</Role>
      <ShortName>Subsequent Events - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="amlx-20260331.htm">amlx-20260331.htm</File>
    <File>amlx-20260331.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="344">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
