<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.2.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>249</ContextCount>
  <ElementCount>340</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>86</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Condensed Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedBalanceSheets</Role>
      <ShortName>Condensed Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Condensed Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Condensed Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedStatementsOfOperations</Role>
      <ShortName>Condensed Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Condensed Statements of Operations (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedStatementsOfOperationsParenthetical</Role>
      <ShortName>Condensed Statements of Operations (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Condensed Statements of Changes in Stockholders' (Deficit) Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedStatementsOfChangesInStockholdersDeficitEquity</Role>
      <ShortName>Condensed Statements of Changes in Stockholders' (Deficit) Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Statement - Condensed Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/StatementCondensedStatementsOfCashFlows</Role>
      <ShortName>Condensed Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Nature of Operations and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNatureOfOperationsAndBasisOfPresentation</Role>
      <ShortName>Nature of Operations and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPolicies</Role>
      <ShortName>Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Property and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosurePropertyAndEquipment</Role>
      <ShortName>Property and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Accrued Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureAccruedExpenses</Role>
      <ShortName>Accrued Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureDebt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Stockholders' (Deficit) Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquity</Role>
      <ShortName>Stockholders' (Deficit) Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Net Loss Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShare</Role>
      <ShortName>Net Loss Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPolicies</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPoliciesTables</Role>
      <ShortName>Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPolicies</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Property and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosurePropertyAndEquipmentTables</Role>
      <ShortName>Property and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosurePropertyAndEquipment</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Accrued Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureAccruedExpensesTables</Role>
      <ShortName>Accrued Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureAccruedExpenses</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureLeases</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Stockholders' (Deficit) Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityTables</Role>
      <ShortName>Stockholders' (Deficit) Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquity</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Net Loss Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShareTables</Role>
      <ShortName>Net Loss Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShare</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Nature of Operations and Basis of Presentation - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNatureOfOperationsAndBasisOfPresentationAdditionalInformationDetails</Role>
      <ShortName>Nature of Operations and Basis of Presentation - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Significant Accounting Policies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPoliciesAdditionalInformationDetails</Role>
      <ShortName>Significant Accounting Policies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Significant Accounting Policies - Schedule of Estimate Fair Value of Stock Options Granted (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSignificantAccountingPoliciesScheduleOfEstimateFairValueOfStockOptionsGrantedDetails</Role>
      <ShortName>Significant Accounting Policies - Schedule of Estimate Fair Value of Stock Options Granted (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Property and Equipment - Schedule of Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosurePropertyAndEquipmentScheduleOfPropertyAndEquipmentDetails</Role>
      <ShortName>Property and Equipment - Schedule of Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Accrued Expenses - Schedule of Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureAccruedExpensesScheduleOfAccruedExpensesDetails</Role>
      <ShortName>Accrued Expenses - Schedule of Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Leases - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureLeasesAdditionalInformationDetails</Role>
      <ShortName>Leases - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Leases - Reconciliation of Undiscounted Lease Liabilities to Total Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureLeasesReconciliationOfUndiscountedLeaseLiabilitiesToTotalLeaseLiabilitiesDetails</Role>
      <ShortName>Leases - Reconciliation of Undiscounted Lease Liabilities to Total Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Debt - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureDebtAdditionalInformationDetails</Role>
      <ShortName>Debt - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfAssetsAndLiabilitiesMeasuredAtFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Fair Value Measurements - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurementsAdditionalInformationDetails</Role>
      <ShortName>Fair Value Measurements - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Fair Value Measurements - Schedule of Change in Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureFairValueMeasurementsScheduleOfChangeInFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Schedule of Change in Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Commitments and Contingencies - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetails</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Stockholders' (Deficit) Equity - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityAdditionalInformationDetails</Role>
      <ShortName>Stockholders' (Deficit) Equity - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Stockholders' (Deficit) Equity - Summary of Option Activity under 2018 Plan, 2013 Plan and 2010 Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquitySummaryOfOptionActivityUnder2018Plan2013PlanAnd2010PlanDetails</Role>
      <ShortName>Stockholders' (Deficit) Equity - Summary of Option Activity under 2018 Plan, 2013 Plan and 2010 Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Stockholders' (Deficit) Equity - Summary of Stock-Based Compensation Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquitySummaryOfStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stockholders' (Deficit) Equity - Summary of Stock-Based Compensation Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Stockholders' (Deficit) Equity - Summary of Warrant Issued (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquitySummaryOfWarrantIssuedDetails</Role>
      <ShortName>Stockholders' (Deficit) Equity - Summary of Warrant Issued (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.acertx.com/20220930/taxonomy/role/DisclosureStockholdersDeficitEquityTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Net Loss Per Share - Schedule of Numerator and Denominator used in Calculation of Basic and Diluted Net Loss Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShareScheduleOfNumeratorAndDenominatorUsedInCalculationOfBasicAndDilutedNetLossPerCommonShareDetails</Role>
      <ShortName>Net Loss Per Share - Schedule of Numerator and Denominator used in Calculation of Basic and Diluted Net Loss Per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Net Loss Per Share - Schedule of Numerator and Denominator used in Calculation of Basic and Diluted Net Loss Per Common Share (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShareScheduleOfNumeratorAndDenominatorUsedInCalculationOfBasicAndDilutedNetLossPerCommonShareParentheticalDetails</Role>
      <ShortName>Net Loss Per Share - Schedule of Numerator and Denominator used in Calculation of Basic and Diluted Net Loss Per Common Share (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Net Loss Per Share - Schedule of Number of Shares of Common Stock Underlying Potentially Dilutive Securities Excluded From Calculation of Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShareScheduleOfNumberOfSharesOfCommonStockUnderlyingPotentiallyDilutiveSecuritiesExcludedFromCalculationOfDilutedNetLossPerShareDetails</Role>
      <ShortName>Net Loss Per Share - Schedule of Number of Shares of Common Stock Underlying Potentially Dilutive Securities Excluded From Calculation of Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Net Loss Per Share - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureNetLossPerShareAdditionalInformationDetails</Role>
      <ShortName>Net Loss Per Share - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="acer-10q_20220930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Subsequent Events - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.acertx.com/20220930/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails</Role>
      <ShortName>Subsequent Events - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Warning">[ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 27 fact(s) appearing in ix:hidden were eligible for transformation: acer:DebtInstrumentRepaymentPercentageOnOutstandingPrincipalAmount, acer:DebtInstrumentRepaymentPercentageOnOutstandingPrincipalPlusAnyAndAllPaidInKindInterestAmount, acer:ThresholdNumberOfBusinessDaysForMarketValueOfListedSecurities, acer:ThresholdNumberOfCalendarDaysToRegainCompliance, us-gaap:ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted, us-gaap:ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate, us-gaap:ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect, us-gaap:LesseeOperatingLeaseExistenceOfOptionToExtend, us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1, us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate, us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum, us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum, us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1, us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1, us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2 -  acer-10q_20220930.htm 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59</Log>
    <Log type="Warning">[ix-0514-Hidden-Fact-Not-Referenced] WARN: 6 fact(s) appearing in ix:hidden were not referenced by any -sec-ix-hidden style property: us-gaap:OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseLiabilityStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList -  acer-10q_20220930.htm 35, 36, 45, 46, 47, 48</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="acer-10q_20220930.htm">acer-10q_20220930.htm</File>
    <File>acer-20220930.xsd</File>
    <File>acer-20220930_cal.xml</File>
    <File>acer-20220930_def.xml</File>
    <File>acer-20220930_lab.xml</File>
    <File>acer-20220930_pre.xml</File>
    <File>acer-ex311_7.htm</File>
    <File>acer-ex312_8.htm</File>
    <File>acer-ex321_6.htm</File>
    <File>acer-ex322_9.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>gugbkuksx34m000001.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="560">http://fasb.org/us-gaap/2022</BaseTaxonomy>
    <BaseTaxonomy items="31">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
