<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.22.4</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>210</ContextCount>
  <ElementCount>354</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>75</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>4</UnitCount>
  <MyReports>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>00090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>00100 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>00105 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>00200 - Statement - Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedStatementsOfOperations</Role>
      <ShortName>Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>00300 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>00400 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>00500 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>10101 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureBasisOfPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>10201 - Disclosure - New Accounting Pronouncements and Changes in Accounting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureNewAccountingPronouncementsAndChangesInAccounting</Role>
      <ShortName>New Accounting Pronouncements and Changes in Accounting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>10301 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssets</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>10401 - Disclosure - Revenue Recognition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognition</Role>
      <ShortName>Revenue Recognition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>10501 - Disclosure - Joint Ventures and Variable Interest Entities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntities</Role>
      <ShortName>Joint Ventures and Variable Interest Entities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>10601 - Disclosure - Pension Benefit Obligations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosurePensionBenefitObligations</Role>
      <ShortName>Pension Benefit Obligations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>10701 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>10801 - Disclosure - Derivative Financial Instruments and Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDerivativeFinancialInstrumentsAndFairValueMeasurements</Role>
      <ShortName>Derivative Financial Instruments and Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>10901 - Disclosure - Share-Based Payments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureShareBasedPayments</Role>
      <ShortName>Share-Based Payments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>11001 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>11101 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>11201 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>11301 - Disclosure - Other Financial Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureOtherFinancialInformation</Role>
      <ShortName>Other Financial Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>11401 - Disclosure - Reclassifications out of Accumulated Other Comprehensive Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveLoss</Role>
      <ShortName>Reclassifications out of Accumulated Other Comprehensive Loss</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>11501 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>11601 - Disclosure - Reportable Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReportableSegments</Role>
      <ShortName>Reportable Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>30303 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsTables</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssets</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>30403 - Disclosure - Revenue Recognition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognitionTables</Role>
      <ShortName>Revenue Recognition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureRevenueRecognition</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>30503 - Disclosure - Joint Ventures and Variable Interest Entities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntitiesTables</Role>
      <ShortName>Joint Ventures and Variable Interest Entities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntities</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>30603 - Disclosure - Pension Benefit Obligations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosurePensionBenefitObligationsTables</Role>
      <ShortName>Pension Benefit Obligations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosurePensionBenefitObligations</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>30703 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureDebt</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>30803 - Disclosure - Derivative Financial Instruments and Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDerivativeFinancialInstrumentsAndFairValueMeasurementsTables</Role>
      <ShortName>Derivative Financial Instruments and Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureDerivativeFinancialInstrumentsAndFairValueMeasurements</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>30903 - Disclosure - Share-based Payments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureShareBasedPaymentsTables</Role>
      <ShortName>Share-based Payments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>31103 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureEarningsPerShare</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>31203 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureLeases</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>31303 - Disclosure - Other Financial Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureOtherFinancialInformationTables</Role>
      <ShortName>Other Financial Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureOtherFinancialInformation</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>31403 - Disclosure - Reclassifications out of Accumulated Other Comprehensive Loss (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveLossTables</Role>
      <ShortName>Reclassifications out of Accumulated Other Comprehensive Loss (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveLoss</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>31603 - Disclosure - Reportable Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReportableSegmentsTables</Role>
      <ShortName>Reportable Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureReportableSegments</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>40101 - Disclosure - Basis of Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureBasisOfPresentationDetails</Role>
      <ShortName>Basis of Presentation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureBasisOfPresentation</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>40201 - Disclosure - New Accounting Pronouncements and Changes in Accounting (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureNewAccountingPronouncementsAndChangesInAccountingDetails</Role>
      <ShortName>New Accounting Pronouncements and Changes in Accounting (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>40301 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Sale of businesses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsSaleOfBusinessesDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Sale of businesses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>40302 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Balance sheet (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsBalanceSheetDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Balance sheet (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>40303 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Income Statement Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsIncomeStatementInformationDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Income Statement Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>40304 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Statement of Cash Flows (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsStatementOfCashFlowsDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Statement of Cash Flows (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>40305 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Goodwill by segments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsGoodwillBySegmentsDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Goodwill by segments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>40306 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsIntangibleAssetsDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>40307 - Disclosure - Discontinued Operations, Goodwill and Intangible Assets - Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDiscontinuedOperationsGoodwillAndIntangibleAssetsAmortizationExpenseDetails</Role>
      <ShortName>Discontinued Operations, Goodwill and Intangible Assets - Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>40401 - Disclosure - Revenue Recognition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognitionDetails</Role>
      <ShortName>Revenue Recognition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureRevenueRecognitionTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>40402 - Disclosure - Revenue Recognition - Disaggregated revenues (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognitionDisaggregatedRevenuesDetails</Role>
      <ShortName>Revenue Recognition - Disaggregated revenues (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>40403 - Disclosure - Revenue Recognition - Performance obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognitionPerformanceObligationsDetails</Role>
      <ShortName>Revenue Recognition - Performance obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>40404 - Disclosure - Revenue Recognition - Accounts receivable, net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureRevenueRecognitionAccountsReceivableNetDetails</Role>
      <ShortName>Revenue Recognition - Accounts receivable, net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>40501 - Disclosure - Joint Ventures and Variable Interest Entities - Consolidated (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntitiesConsolidatedDetails</Role>
      <ShortName>Joint Ventures and Variable Interest Entities - Consolidated (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>40502 - Disclosure - Joint Ventures and Variable Interest Entities - Unconsolidated (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntitiesUnconsolidatedDetails</Role>
      <ShortName>Joint Ventures and Variable Interest Entities - Unconsolidated (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>40503 - Disclosure - Joint Ventures and Variable Interest Entities - Equity in Earnings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureJointVenturesAndVariableInterestEntitiesEquityInEarningsDetails</Role>
      <ShortName>Joint Ventures and Variable Interest Entities - Equity in Earnings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>40601 - Disclosure - Pension Benefit Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosurePensionBenefitObligationsDetails</Role>
      <ShortName>Pension Benefit Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosurePensionBenefitObligationsTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>40701 - Disclosure - Debt - Long-term debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtLongTermDebtDetails</Role>
      <ShortName>Debt - Long-term debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>40702 - Disclosure - Debt - Scheduled Maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtScheduledMaturitiesDetails</Role>
      <ShortName>Debt - Scheduled Maturities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>40703 - Disclosure - Debt - Credit Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtCreditAgreementDetails</Role>
      <ShortName>Debt - Credit Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>40704 - Disclosure - Debt - 2027 Senior Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebt2027SeniorNotesDetails</Role>
      <ShortName>Debt - 2027 Senior Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>40705 - Disclosure - Debt - Other Debt and Other Items (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtOtherDebtAndOtherItemsDetails</Role>
      <ShortName>Debt - Other Debt and Other Items (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>40706 - Disclosure - Debt - Effective Interest Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDebtEffectiveInterestRateDetails</Role>
      <ShortName>Debt - Effective Interest Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>40801 - Disclosure - Derivative Financial Instruments and Fair Value Measurements - Cash Flow Hedges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDerivativeFinancialInstrumentsAndFairValueMeasurementsCashFlowHedgesDetails</Role>
      <ShortName>Derivative Financial Instruments and Fair Value Measurements - Cash Flow Hedges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>40802 - Disclosure - Derivative Financial Instruments and Fair Value Measurements - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureDerivativeFinancialInstrumentsAndFairValueMeasurementsFairValueMeasurementsDetails</Role>
      <ShortName>Derivative Financial Instruments and Fair Value Measurements - Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>40901 - Disclosure - Share-Based Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureShareBasedPaymentsDetails</Role>
      <ShortName>Share-Based Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureShareBasedPayments</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>41001 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureIncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>41101 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureEarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureEarningsPerShareTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>41201 - Disclosure - Leases - Components of lease expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesComponentsOfLeaseExpenseDetails</Role>
      <ShortName>Leases - Components of lease expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>41202 - Disclosure - Leases - Additional balance sheet information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesAdditionalBalanceSheetInformationDetails</Role>
      <ShortName>Leases - Additional balance sheet information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>41203 - Disclosure - Leases - Additional cash flow information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesAdditionalCashFlowInformationDetails</Role>
      <ShortName>Leases - Additional cash flow information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>41204 - Disclosure - Leases - Lease payments under operating lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesLeasePaymentsUnderOperatingLeaseDetails</Role>
      <ShortName>Leases - Lease payments under operating lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>41205 - Disclosure - Leases - Lease payments under finance lease (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureLeasesLeasePaymentsUnderFinanceLeaseDetails</Role>
      <ShortName>Leases - Lease payments under finance lease (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>41301 - Disclosure - Other Financial Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureOtherFinancialInformationDetails</Role>
      <ShortName>Other Financial Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureOtherFinancialInformationTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>41401 - Disclosure - Reclassifications out of Accumulated Other Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>Reclassifications out of Accumulated Other Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureReclassificationsOutOfAccumulatedOtherComprehensiveLossTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>41501 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureCommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.aecom.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="acm-20221231x10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>41601 - Disclosure - Reportable Segments and Geographic Information - Summarized financial information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.aecom.com/role/DisclosureReportableSegmentsAndGeographicInformationSummarizedFinancialInformationDetails</Role>
      <ShortName>Reportable Segments and Geographic Information - Summarized financial information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</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: 2 fact(s) appearing in ix:hidden were eligible for transformation: us-gaap:CommonStockSharesOutstanding -  acm-20221231x10q.htm 9</Log>
    <Log type="Warning">[ix-0514-Hidden-Fact-Not-Referenced] WARN: 8 fact(s) appearing in ix:hidden were not referenced by any -sec-ix-hidden style property: us-gaap:CommitmentsAndContingencies, us-gaap:FinanceLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList, us-gaap:FinanceLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList, us-gaap:FinanceLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList, us-gaap:OperatingLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList -  acm-20221231x10q.htm 9</Log>
  </Logs>
  <InputFiles>
    <File doctype="10-Q" original="acm-20221231x10q.htm">acm-20221231x10q.htm</File>
    <File>acm-20221231.xsd</File>
    <File>acm-20221231_cal.xml</File>
    <File>acm-20221231_def.xml</File>
    <File>acm-20221231_lab.xml</File>
    <File>acm-20221231_pre.xml</File>
    <File>acm-20221231xex10d1.htm</File>
    <File>acm-20221231xex10d2.htm</File>
    <File>acm-20221231xex31d1.htm</File>
    <File>acm-20221231xex31d2.htm</File>
    <File>acm-20221231xex32.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="794">http://fasb.org/us-gaap/2022</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2022</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
