<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>372</ContextCount>
  <ElementCount>424</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>113</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>19</UnitCount>
  <MyReports>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>995200090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>995200100 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>995200200 - Statement - Consolidated Statements of Income/(Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/StatementConsolidatedStatementsOfIncomeLoss</Role>
      <ShortName>Consolidated Statements of Income/(Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>995200300 - Statement - Consolidated Statements of Comprehensive Income/(Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/StatementConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>Consolidated Statements of Comprehensive Income/(Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>995200400 - Statement - Consolidated Statements of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/StatementConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>Consolidated Statements of Changes in Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>995200500 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>995210101 - Disclosure - General information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureGeneralInformation</Role>
      <ShortName>General information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995210201 - Disclosure - Basis of preparation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureBasisOfPreparation</Role>
      <ShortName>Basis of preparation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995210301 - Disclosure - Summary of material accounting policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPolicies</Role>
      <ShortName>Summary of material accounting policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995210401 - Disclosure - Property, plant and equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePropertyPlantAndEquipment</Role>
      <ShortName>Property, plant and equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995210501 - Disclosure - Right-of-use assets, long-term financial assets and lease liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilities</Role>
      <ShortName>Right-of-use assets, long-term financial assets and lease liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995210601 - Disclosure - Intangible assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIntangibleAssets</Role>
      <ShortName>Intangible assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995210701 - Disclosure - Cash and cash equivalents and short-term financial assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCashAndCashEquivalentsAndShortTermFinancialAssets</Role>
      <ShortName>Cash and cash equivalents and short-term financial assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995210801 - Disclosure - Prepaid expenses and accrued income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePrepaidExpensesAndAccruedIncome</Role>
      <ShortName>Prepaid expenses and accrued income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995210901 - Disclosure - Restructuring</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRestructuring</Role>
      <ShortName>Restructuring</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995211001 - Disclosure - Other current receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureOtherCurrentReceivables</Role>
      <ShortName>Other current receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995211101 - Disclosure - Share capital</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapital</Role>
      <ShortName>Share capital</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995211201 - Disclosure - Trade and other payables and accrued expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureTradeAndOtherPayablesAndAccruedExpenses</Role>
      <ShortName>Trade and other payables and accrued expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995211301 - Disclosure - Contract revenues</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenues</Role>
      <ShortName>Contract revenues</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995211401 - Disclosure - Expenses by category</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureExpensesByCategory</Role>
      <ShortName>Expenses by category</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995211501 - Disclosure - Related-party transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRelatedPartyTransactions</Role>
      <ShortName>Related-party transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995211601 - Disclosure - Income taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995211701 - Disclosure - Retirement benefit plan</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlan</Role>
      <ShortName>Retirement benefit plan</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995211801 - Disclosure - Share-based compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensation</Role>
      <ShortName>Share-based compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995211901 - Disclosure - Commitments and contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995212001 - Disclosure - Earnings per share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureEarningsPerShare</Role>
      <ShortName>Earnings per share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995212101 - Disclosure - Financial instruments and risk management</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureFinancialInstrumentsAndRiskManagement</Role>
      <ShortName>Financial instruments and risk management</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995212201 - Disclosure - Capital risk management</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCapitalRiskManagement</Role>
      <ShortName>Capital risk management</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995212301 - Disclosure - Subsequent events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>99920302 - Disclosure - Summary of material accounting policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesPolicies</Role>
      <ShortName>Summary of material accounting policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>99930303 - Disclosure - Summary of material accounting policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesTables</Role>
      <ShortName>Summary of material accounting policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPolicies</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>99930403 - Disclosure - Property, plant and equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePropertyPlantAndEquipmentTables</Role>
      <ShortName>Property, plant and equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosurePropertyPlantAndEquipment</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>99930503 - Disclosure - Right-of-use assets, long-term financial assets and lease liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilitiesTables</Role>
      <ShortName>Right-of-use assets, long-term financial assets and lease liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilities</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>99930603 - Disclosure - Intangible assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIntangibleAssetsTables</Role>
      <ShortName>Intangible assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureIntangibleAssets</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>99930703 - Disclosure - Cash and cash equivalents and short-term financial assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCashAndCashEquivalentsAndShortTermFinancialAssetsTables</Role>
      <ShortName>Cash and cash equivalents and short-term financial assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureCashAndCashEquivalentsAndShortTermFinancialAssets</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>99930803 - Disclosure - Prepaid expenses and accrued income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePrepaidExpensesAndAccruedIncomeTables</Role>
      <ShortName>Prepaid expenses and accrued income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosurePrepaidExpensesAndAccruedIncome</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>99931003 - Disclosure - Other current receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureOtherCurrentReceivablesTables</Role>
      <ShortName>Other current receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureOtherCurrentReceivables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>99931103 - Disclosure - Share capital (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalTables</Role>
      <ShortName>Share capital (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureShareCapital</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>99931203 - Disclosure - Trade and other payables and accrued expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureTradeAndOtherPayablesAndAccruedExpensesTables</Role>
      <ShortName>Trade and other payables and accrued expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureTradeAndOtherPayablesAndAccruedExpenses</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>99931303 - Disclosure - Contract revenues (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesTables</Role>
      <ShortName>Contract revenues (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureContractRevenues</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>99931403 - Disclosure - Expenses by category (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureExpensesByCategoryTables</Role>
      <ShortName>Expenses by category (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureExpensesByCategory</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>99931503 - Disclosure - Related-party transactions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRelatedPartyTransactionsTables</Role>
      <ShortName>Related-party transactions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRelatedPartyTransactions</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>99931603 - Disclosure - Income taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIncomeTaxesTables</Role>
      <ShortName>Income taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>99931703 - Disclosure - Retirement benefit plan (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanTables</Role>
      <ShortName>Retirement benefit plan (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRetirementBenefitPlan</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>99931803 - Disclosure - Share-based compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationTables</Role>
      <ShortName>Share-based compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureShareBasedCompensation</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>99931903 - Disclosure - Commitments and contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>99932003 - Disclosure - Earnings per share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings per share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureEarningsPerShare</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>99932103 - Disclosure - Financial instruments and risk management (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureFinancialInstrumentsAndRiskManagementTables</Role>
      <ShortName>Financial instruments and risk management (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureFinancialInstrumentsAndRiskManagement</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>99940101 - Disclosure - General information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureGeneralInformationDetails</Role>
      <ShortName>General information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureGeneralInformation</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>99940201 - Disclosure - Basis of preparation - Going concern (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureBasisOfPreparationGoingConcernDetails</Role>
      <ShortName>Basis of preparation - Going concern (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>99940301 - Disclosure - Summary of material accounting policies - Functional and reporting currency (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesFunctionalAndReportingCurrencyDetails</Role>
      <ShortName>Summary of material accounting policies - Functional and reporting currency (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>99940302 - Disclosure - Summary of material accounting policies, Right-of-use assets and lease liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesRightOfUseAssetsAndLeaseLiabilitiesDetails</Role>
      <ShortName>Summary of material accounting policies, Right-of-use assets and lease liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>99940303 - Disclosure - Summary of material accounting policies, Property, plant and equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesPropertyPlantAndEquipmentDetails</Role>
      <ShortName>Summary of material accounting policies, Property, plant and equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>99940304 - Disclosure - Summary of material accounting policies, Income taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesIncomeTaxesDetails</Role>
      <ShortName>Summary of material accounting policies, Income taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>99940305 - Disclosure - Summary of material accounting policies, Segment reporting (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureSummaryOfMaterialAccountingPoliciesSegmentReportingDetails</Role>
      <ShortName>Summary of material accounting policies, Segment reporting (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>99940401 - Disclosure - Property, plant and equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePropertyPlantAndEquipmentDetails</Role>
      <ShortName>Property, plant and equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosurePropertyPlantAndEquipmentTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>99940501 - Disclosure - Right-of-use assets, long-term financial assets and lease liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilitiesDetails</Role>
      <ShortName>Right-of-use assets, long-term financial assets and lease liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilitiesTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>99940502 - Disclosure - Right-of-use assets, long-term financial assets and lease liabilities - Statement of income/(loss) and cash flow (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilitiesStatementOfIncomeLossAndCashFlowDetails</Role>
      <ShortName>Right-of-use assets, long-term financial assets and lease liabilities - Statement of income/(loss) and cash flow (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>99940503 - Disclosure - Right-of-use assets, long-term financial assets and lease liabilities - Contractual undiscounted cash flows for lease obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRightOfUseAssetsLongTermFinancialAssetsAndLeaseLiabilitiesContractualUndiscountedCashFlowsForLeaseObligationsDetails</Role>
      <ShortName>Right-of-use assets, long-term financial assets and lease liabilities - Contractual undiscounted cash flows for lease obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>99940601 - Disclosure - Intangible assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIntangibleAssetsDetails</Role>
      <ShortName>Intangible assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureIntangibleAssetsTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>99940701 - Disclosure - Cash and cash equivalents and financial assets - Cash and cash equivalents (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCashAndCashEquivalentsAndFinancialAssetsCashAndCashEquivalentsDetails</Role>
      <ShortName>Cash and cash equivalents and financial assets - Cash and cash equivalents (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>99940702 - Disclosure - Cash and cash equivalents and short-term financial assets - Short-term financial assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCashAndCashEquivalentsAndShortTermFinancialAssetsShortTermFinancialAssetsDetails</Role>
      <ShortName>Cash and cash equivalents and short-term financial assets - Short-term financial assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>99940801 - Disclosure - Prepaid expenses and accrued income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosurePrepaidExpensesAndAccruedIncomeDetails</Role>
      <ShortName>Prepaid expenses and accrued income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosurePrepaidExpensesAndAccruedIncomeTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>99940901 - Disclosure - Restructuring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRestructuringDetails</Role>
      <ShortName>Restructuring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRestructuring</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>99941001 - Disclosure - Other current receivables (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureOtherCurrentReceivablesDetails</Role>
      <ShortName>Other current receivables (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureOtherCurrentReceivablesTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>99941101 - Disclosure - Share capital - Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalNarrativesDetails</Role>
      <ShortName>Share capital - Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>99941102 - Disclosure - Share capital - Capital Structure (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalCapitalStructureDetails</Role>
      <ShortName>Share capital - Capital Structure (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>99941103 - Disclosure - Share capital - Authorized capital (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalAuthorizedCapitalDetails</Role>
      <ShortName>Share capital - Authorized capital (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>99941104 - Disclosure - Share capital - Conditional share capital for financing and other purposes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalConditionalShareCapitalForFinancingAndOtherPurposesDetails</Role>
      <ShortName>Share capital - Conditional share capital for financing and other purposes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>99941105 - Disclosure - Share capital - Conditional share capital for employee benefit plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalConditionalShareCapitalForEmployeeBenefitPlansDetails</Role>
      <ShortName>Share capital - Conditional share capital for employee benefit plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>99941106 - Disclosure - Share capital - Follow-On Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalFollowOnOfferingDetails</Role>
      <ShortName>Share capital - Follow-On Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>99941107 - Disclosure - Share capital - Shelf registration statement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalShelfRegistrationStatementDetails</Role>
      <ShortName>Share capital - Shelf registration statement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>99941108 - Disclosure - Share capital - At the market equity offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareCapitalAtMarketEquityOfferingDetails</Role>
      <ShortName>Share capital - At the market equity offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>99941201 - Disclosure - Trade and other payables and accrued expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureTradeAndOtherPayablesAndAccruedExpensesDetails</Role>
      <ShortName>Trade and other payables and accrued expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureTradeAndOtherPayablesAndAccruedExpensesTables</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>99941301 - Disclosure - Contract revenues - Contract Revenue Attributable to Licensing Arrangements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesContractRevenueAttributableToLicensingArrangementsDetails</Role>
      <ShortName>Contract revenues - Contract Revenue Attributable to Licensing Arrangements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>99941302 - Disclosure - Contract revenues - Recognized Revenues (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesRecognizedRevenuesDetails</Role>
      <ShortName>Contract revenues - Recognized Revenues (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>99941303 - Disclosure - Contract revenues - Morphomer Tau small molecule - 2018 license agreement with Eli Lilly and Company (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesMorphomerTauSmallMolecule2018LicenseAgreementWithEliLillyAndCompanyDetails</Role>
      <ShortName>Contract revenues - Morphomer Tau small molecule - 2018 license agreement with Eli Lilly and Company (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>99941304 - Disclosure - Contract revenues - Tau Vaccine in AD - 2014 Agreement with Janssen Pharmaceuticals (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesTauVaccineInAd2014AgreementWithJanssenPharmaceuticalsDetails</Role>
      <ShortName>Contract revenues - Tau Vaccine in AD - 2014 Agreement with Janssen Pharmaceuticals (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>99941305 - Disclosure - Contract revenues - Tau-PET imaging agent -2014 Agreement with Life Molecular Imaging (formerly Piramal Imaging SA) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesTauPetImagingAgent2014AgreementWithLifeMolecularImagingFormerlyPiramalImagingSaDetails</Role>
      <ShortName>Contract revenues - Tau-PET imaging agent -2014 Agreement with Life Molecular Imaging (formerly Piramal Imaging SA) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>99941306 - Disclosure - Contract revenues - Anti-Abeta Active Immunotherapy in AD - 2024 agreement Takeda Pharmaceuticals, USA Inc. (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesAntiAbetaActiveImmunotherapyInAd2024AgreementTakedaPharmaceuticalsUsaIncDetails</Role>
      <ShortName>Contract revenues - Anti-Abeta Active Immunotherapy in AD - 2024 agreement Takeda Pharmaceuticals, USA Inc. (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>99941307 - Disclosure - Contract revenues - Grants from the Michael J. Fox Foundation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureContractRevenuesGrantsFromMichaelJFoxFoundationDetails</Role>
      <ShortName>Contract revenues - Grants from the Michael J. Fox Foundation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>99941401 - Disclosure - Expenses by category (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureExpensesByCategoryDetails</Role>
      <ShortName>Expenses by category (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureExpensesByCategoryTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>99941501 - Disclosure - Related-party transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRelatedPartyTransactionsDetails</Role>
      <ShortName>Related-party transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureRelatedPartyTransactionsTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>99941601 - Disclosure - Income taxes - Summary of Income Tax Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIncomeTaxesSummaryOfIncomeTaxExpenseDetails</Role>
      <ShortName>Income taxes - Summary of Income Tax Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>99941602 - Disclosure - Income taxes, Unrecognized Deductible Temporary Differences, Unused Tax Losses and Unused Tax Credits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureIncomeTaxesUnrecognizedDeductibleTemporaryDifferencesUnusedTaxLossesAndUnusedTaxCreditsDetails</Role>
      <ShortName>Income taxes, Unrecognized Deductible Temporary Differences, Unused Tax Losses and Unused Tax Credits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>99941701 - Disclosure - Retirement benefit plan - Summary of Benefit Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanSummaryOfBenefitPlanDetails</Role>
      <ShortName>Retirement benefit plan - Summary of Benefit Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>99941702 - Disclosure - Retirement benefit plan - Amounts recorded in consolidated statements of income (loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanAmountsRecordedInConsolidatedStatementsOfIncomeLossDetails</Role>
      <ShortName>Retirement benefit plan - Amounts recorded in consolidated statements of income (loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>99941703 - Disclosure - Retirement benefit plan - Changes in Defined Benefit Obligation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanChangesInDefinedBenefitObligationDetails</Role>
      <ShortName>Retirement benefit plan - Changes in Defined Benefit Obligation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>99941704 - Disclosure - Retirement benefit plan - Changes in Fair Value of Plan Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanChangesInFairValueOfPlanAssetsDetails</Role>
      <ShortName>Retirement benefit plan - Changes in Fair Value of Plan Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>99941705 - Disclosure - Retirement benefit plan - Change in Net Defined Benefit Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanChangeInNetDefinedBenefitLiabilityDetails</Role>
      <ShortName>Retirement benefit plan - Change in Net Defined Benefit Liability (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>99941706 - Disclosure - Retirement benefit plan - Change in other comprehensive gains (losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanChangeInOtherComprehensiveGainsLossesDetails</Role>
      <ShortName>Retirement benefit plan - Change in other comprehensive gains (losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>99941707 - Disclosure - Retirement benefit plan - Actuarial Assumptions and Sensitivity Analysis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureRetirementBenefitPlanActuarialAssumptionsAndSensitivityAnalysisDetails</Role>
      <ShortName>Retirement benefit plan - Actuarial Assumptions and Sensitivity Analysis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>99941801 - Disclosure - Share-based compensation, Plans Outstanding (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationPlansOutstandingDetails</Role>
      <ShortName>Share-based compensation, Plans Outstanding (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>99941802 - Disclosure - Share-based compensation - Options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationOptionsDetails</Role>
      <ShortName>Share-based compensation - Options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>99941803 - Disclosure - Share-based compensation, Outstanding Options, Range of Exercise prices and Expiration Dates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationOutstandingOptionsRangeOfExercisePricesAndExpirationDatesDetails</Role>
      <ShortName>Share-based compensation, Outstanding Options, Range of Exercise prices and Expiration Dates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>99941804 - Disclosure - Share-based compensation, Weighted Average Grant date Fair Value and Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationWeightedAverageGrantDateFairValueAndAssumptionsDetails</Role>
      <ShortName>Share-based compensation, Weighted Average Grant date Fair Value and Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>99941805 - Disclosure - Share-based compensation, Non-vested Share Awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureShareBasedCompensationNonVestedShareAwardsDetails</Role>
      <ShortName>Share-based compensation, Non-vested Share Awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>99941901 - Disclosure - Commitments and contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureCommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>100</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>99942001 - Disclosure - Earnings per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureEarningsPerShareDetails</Role>
      <ShortName>Earnings per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>101</Position>
    </Report>
    <Report instance="aciu-20251231x20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>99942101 - Disclosure - Financial instruments and risk management (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://acimume.com/role/DisclosureFinancialInstrumentsAndRiskManagementDetails</Role>
      <ShortName>Financial instruments and risk management (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://acimume.com/role/DisclosureFinancialInstrumentsAndRiskManagementTables</ParentRole>
      <Position>102</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>aciu-20251231.xsd</File>
    <File>aciu-20251231_cal.xml</File>
    <File>aciu-20251231_def.xml</File>
    <File>aciu-20251231_lab.xml</File>
    <File>aciu-20251231_pre.xml</File>
    <File doctype="20-F" isDefinitelyFs="true" isIfrs="true" isUsgaap="true" original="aciu-20251231x20f.htm">aciu-20251231x20f.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>aciu-20251231x20f001.jpg</File>
    <File>aciu-20251231x20f002.jpg</File>
    <File>aciu-20251231x20f003.jpg</File>
    <File>aciu-20251231x20f004.jpg</File>
    <File>aciu-20251231x20f005.jpg</File>
    <File>aciu-20251231x20f006.jpg</File>
    <File>aciu-20251231x20f007.jpg</File>
    <File>aciu-20251231x20f008.jpg</File>
    <File>aciu-20251231x20f009.jpg</File>
    <File>aciu-20251231x20f010.jpg</File>
    <File>aciu-20251231x20f011.jpg</File>
    <File>aciu-20251231x20f012.jpg</File>
    <File>aciu-20251231x20f013.jpg</File>
    <File>aciu-20251231x20f014.jpg</File>
    <File>aciu-20251231x20f015.jpg</File>
    <File>aciu-20251231x20f016.jpg</File>
    <File>aciu-20251231x20f017.jpg</File>
    <File>aciu-20251231x20f018.jpg</File>
    <File>aciu-20251231x20f019.jpg</File>
    <File>aciu-20251231x20f020.jpg</File>
    <File>aciu-20251231x20f021.jpg</File>
    <File>aciu-20251231x20f022.jpg</File>
    <File>aciu-20251231x20f023.jpg</File>
    <File>aciu-20251231x20f024.jpg</File>
    <File>aciu-20251231x20f025.jpg</File>
    <File>aciu-20251231x20f026.jpg</File>
    <File>aciu-20251231x20f027.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="15">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="45">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="1">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
    <BaseTaxonomy items="1102">https://xbrl.ifrs.org/taxonomy/2025-03-27/ifrs-full</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
