<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.23.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>381</ContextCount>
  <ElementCount>534</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>107</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0000002 - Document - Audit Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/AuditInformation</Role>
      <ShortName>Audit Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0000003 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0000004 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0000005 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0000006 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0000007 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0000008 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>0000009 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>0000010 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASES</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>0000011 - Disclosure - ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONS</Role>
      <ShortName>ACQUISITIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>0000012 - Disclosure - POSTRETIREMENT BENEFITS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITS</Role>
      <ShortName>POSTRETIREMENT BENEFITS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>0000013 - Disclosure - STOCK INCENTIVE PLAN</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLAN</Role>
      <ShortName>STOCK INCENTIVE PLAN</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>0000014 - Disclosure - OTHER (INCOME) AND EXPENSE, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/OTHERINCOMEANDEXPENSENET</Role>
      <ShortName>OTHER (INCOME) AND EXPENSE, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>0000015 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>0000016 - Disclosure - EARNINGS PER SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/EARNINGSPERSHARE</Role>
      <ShortName>EARNINGS PER SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>0000017 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>0000018 - Disclosure - INVENTORIES, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INVENTORIESNET</Role>
      <ShortName>INVENTORIES, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>0000019 - Disclosure - PROPERTY, PLANT AND EQUIPMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/PROPERTYPLANTANDEQUIPMENT</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>0000020 - Disclosure - GOODWILL AND INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETS</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>0000021 - Disclosure - DEBT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBT</Role>
      <ShortName>DEBT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>0000022 - Disclosure - FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/FAIRVALUEMEASUREMENTS</Role>
      <ShortName>FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>0000023 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/COMMITMENTSANDCONTINGENCIES</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>0000024 - Disclosure - GUARANTEES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GUARANTEES</Role>
      <ShortName>GUARANTEES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>0000025 - Disclosure - SEGMENT INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATION</Role>
      <ShortName>SEGMENT INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>0000026 - Disclosure - SUBSEQUENT EVENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SUBSEQUENTEVENTS</Role>
      <ShortName>SUBSEQUENT EVENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>0000027 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATION</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>0000028 - Disclosure - SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS</Role>
      <ShortName>SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9954471 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9954472 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9954473 - Disclosure - LEASES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESTables</Role>
      <ShortName>LEASES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/LEASES</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9954474 - Disclosure - ACQUISITIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONSTables</Role>
      <ShortName>ACQUISITIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/ACQUISITIONS</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9954475 - Disclosure - POSTRETIREMENT BENEFITS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSTables</Role>
      <ShortName>POSTRETIREMENT BENEFITS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/POSTRETIREMENTBENEFITS</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9954476 - Disclosure - STOCK INCENTIVE PLAN (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANTables</Role>
      <ShortName>STOCK INCENTIVE PLAN (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/STOCKINCENTIVEPLAN</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9954477 - Disclosure - OTHER (INCOME) AND EXPENSE, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables</Role>
      <ShortName>OTHER (INCOME) AND EXPENSE, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/OTHERINCOMEANDEXPENSENET</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9954478 - Disclosure - INCOME TAXES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESTables</Role>
      <ShortName>INCOME TAXES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/INCOMETAXES</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9954479 - Disclosure - EARNINGS PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/EARNINGSPERSHARETables</Role>
      <ShortName>EARNINGS PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/EARNINGSPERSHARE</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9954480 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9954481 - Disclosure - INVENTORIES, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INVENTORIESNETTables</Role>
      <ShortName>INVENTORIES, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/INVENTORIESNET</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9954482 - Disclosure - PROPERTY, PLANT AND EQUIPMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTTables</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/PROPERTYPLANTANDEQUIPMENT</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9954483 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSTables</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETS</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9954484 - Disclosure - DEBT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTTables</Role>
      <ShortName>DEBT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/DEBT</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9954485 - Disclosure - FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/FAIRVALUEMEASUREMENTSTables</Role>
      <ShortName>FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/FAIRVALUEMEASUREMENTS</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9954486 - Disclosure - SEGMENT INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONTables</Role>
      <ShortName>SEGMENT INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://atkore.com/role/SEGMENTINFORMATION</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9954487 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Share Repurchase Program (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESShareRepurchaseProgramDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Share Repurchase Program (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9954488 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRevenueRecognitionDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9954489 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPropertyPlantandEquipmentDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9954490 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Long-Lived Asset and Finite-Lived Intangible Asset Impairments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESLongLivedAssetandFiniteLivedIntangibleAssetImpairmentsDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Long-Lived Asset and Finite-Lived Intangible Asset Impairments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9954491 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Indefinite-Lived Intangible Asset Impairments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESGoodwillandIndefiniteLivedIntangibleAssetImpairmentsDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Indefinite-Lived Intangible Asset Impairments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9954492 - Disclosure - LEASES - Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESAssetsandLiabilitiesDetails</Role>
      <ShortName>LEASES - Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9954493 - Disclosure - LEASES - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESAdditionalInformationDetails</Role>
      <ShortName>LEASES - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9954494 - Disclosure - LEASES - Lease Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESLeaseCostDetails</Role>
      <ShortName>LEASES - Lease Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9954495 - Disclosure - LEASES - Maturity of Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESMaturityofLeaseLiabilitiesDetails</Role>
      <ShortName>LEASES - Maturity of Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9954496 - Disclosure - LEASES - Lease Term and Discount Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/LEASESLeaseTermandDiscountRateDetails</Role>
      <ShortName>LEASES - Lease Term and Discount Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9954497 - Disclosure - ACQUISITIONS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONSNarrativeDetails</Role>
      <ShortName>ACQUISITIONS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9954498 - Disclosure - ACQUISITIONS - Summary of Level 3 Fair Values Assigned to Net Assets Acquired and Liabilities Assumed As of Acquisition Date (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONSSummaryofLevel3FairValuesAssignedtoNetAssetsAcquiredandLiabilitiesAssumedAsofAcquisitionDateDetails</Role>
      <ShortName>ACQUISITIONS - Summary of Level 3 Fair Values Assigned to Net Assets Acquired and Liabilities Assumed As of Acquisition Date (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9954499 - Disclosure - ACQUISITIONS - Summary of Fair Value as of Acquisition Date (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONSSummaryofFairValueasofAcquisitionDateDetails</Role>
      <ShortName>ACQUISITIONS - Summary of Fair Value as of Acquisition Date (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9954500 - Disclosure - ACQUISITIONS - Pro Forma Results (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACQUISITIONSProFormaResultsDetails</Role>
      <ShortName>ACQUISITIONS - Pro Forma Results (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9954501 - Disclosure - POSTRETIREMENT BENEFITS - Net Periodic Benefit Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSNetPeriodicBenefitCostDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Net Periodic Benefit Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9954502 - Disclosure - POSTRETIREMENT BENEFITS - Change in Benefit Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSChangeinBenefitObligationsDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Change in Benefit Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9954503 - Disclosure - POSTRETIREMENT BENEFITS - Benefit Obligation In Excess Of Plan Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSBenefitObligationInExcessOfPlanAssetsDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Benefit Obligation In Excess Of Plan Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9954504 - Disclosure - POSTRETIREMENT BENEFITS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSNarrativeDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9954505 - Disclosure - POSTRETIREMENT BENEFITS - Weighted-Average Asset Allocations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSWeightedAverageAssetAllocationsDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Weighted-Average Asset Allocations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9954506 - Disclosure - POSTRETIREMENT BENEFITS - Asset Allocations by Fair Value Hierarchy (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSAssetAllocationsbyFairValueHierarchyDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Asset Allocations by Fair Value Hierarchy (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9954507 - Disclosure - POSTRETIREMENT BENEFITS - Future Expected Benefit Payments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/POSTRETIREMENTBENEFITSFutureExpectedBenefitPaymentsDetails</Role>
      <ShortName>POSTRETIREMENT BENEFITS - Future Expected Benefit Payments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9954508 - Disclosure - STOCK INCENTIVE PLAN - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANNarrativeDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9954509 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsAssumptionsDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Stock Options Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9954510 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsActivityDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Stock Options Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9954511 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsNarrativeDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Stock Options Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9954512 - Disclosure - STOCK INCENTIVE PLAN - Restricted Stock Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANRestrictedStockNarrativeDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Restricted Stock Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9954513 - Disclosure - STOCK INCENTIVE PLAN - Schedule of Nonvested Restricted Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANScheduleofNonvestedRestrictedStockDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Schedule of Nonvested Restricted Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9954514 - Disclosure - STOCK INCENTIVE PLAN - Performance Share Units Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANPerformanceShareUnitsNarrativeDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Performance Share Units Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9954515 - Disclosure - STOCK INCENTIVE PLAN - Performance Share Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANPerformanceShareAssumptionsDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Performance Share Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9954516 - Disclosure - STOCK INCENTIVE PLAN - Schedule of Nonvested Performance Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/STOCKINCENTIVEPLANScheduleofNonvestedPerformanceSharesDetails</Role>
      <ShortName>STOCK INCENTIVE PLAN - Schedule of Nonvested Performance Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9954517 - Disclosure - OTHER (INCOME) AND EXPENSE, NET (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/OTHERINCOMEANDEXPENSENETDetails</Role>
      <ShortName>OTHER (INCOME) AND EXPENSE, NET (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9954518 - Disclosure - OTHER (INCOME) AND EXPENSE, NET - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/OTHERINCOMEANDEXPENSENETNarrativeDetails</Role>
      <ShortName>OTHER (INCOME) AND EXPENSE, NET - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9954519 - Disclosure - INCOME TAXES - Components of Income (Loss) from Continuing Operations and Income Tax Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESComponentsofIncomeLossfromContinuingOperationsandIncomeTaxExpenseDetails</Role>
      <ShortName>INCOME TAXES - Components of Income (Loss) from Continuing Operations and Income Tax Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9954520 - Disclosure - INCOME TAXES - Differences Between Federal Income Tax Rate and Effective Income Tax Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESDifferencesBetweenFederalIncomeTaxRateandEffectiveIncomeTaxRateDetails</Role>
      <ShortName>INCOME TAXES - Differences Between Federal Income Tax Rate and Effective Income Tax Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9954521 - Disclosure - INCOME TAXES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESNarrativeDetails</Role>
      <ShortName>INCOME TAXES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9954522 - Disclosure - INCOME TAXES - Components of Net Deferred Income Tax Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESComponentsofNetDeferredIncomeTaxAssetsDetails</Role>
      <ShortName>INCOME TAXES - Components of Net Deferred Income Tax Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9954523 - Disclosure - INCOME TAXES - Unrecognized Tax Benefits (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INCOMETAXESUnrecognizedTaxBenefitsDetails</Role>
      <ShortName>INCOME TAXES - Unrecognized Tax Benefits (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9954524 - Disclosure - EARNINGS PER SHARE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/EARNINGSPERSHAREDetails</Role>
      <ShortName>EARNINGS PER SHARE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/EARNINGSPERSHARETables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9954525 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Change in Accumulated Other Comprehensive Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSScheduleofChangeinAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Change in Accumulated Other Comprehensive Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9954526 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary of Amounts Reclassified (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSSummaryofAmountsReclassifiedDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary of Amounts Reclassified (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9954527 - Disclosure - INVENTORIES, NET - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INVENTORIESNETNarrativeDetails</Role>
      <ShortName>INVENTORIES, NET - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9954528 - Disclosure - INVENTORIES, NET - Schedule of Company Inventories (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/INVENTORIESNETScheduleofCompanyInventoriesDetails</Role>
      <ShortName>INVENTORIES, NET - Schedule of Company Inventories (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9954529 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTScheduleofPropertyPlantandEquipmentDetails</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9954530 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTNarrativeDetails</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9954531 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSGoodwillDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9954532 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSNarrativeDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9954533 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSIntangibleAssetsDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9954534 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Expected Amortization Expense (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSExpectedAmortizationExpenseDetails</Role>
      <ShortName>GOODWILL AND INTANGIBLE ASSETS - Expected Amortization Expense (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9954535 - Disclosure - DEBT - Schedule of Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTScheduleofDebtDetails</Role>
      <ShortName>DEBT - Schedule of Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9954536 - Disclosure - DEBT - First Lien Loan - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTFirstLienLoanNarrativeDetails</Role>
      <ShortName>DEBT - First Lien Loan - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9954537 - Disclosure - DEBT - Contractual Obligation Maturities of Long-Term, Fiscal Year Maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTContractualObligationMaturitiesofLongTermFiscalYearMaturityDetails</Role>
      <ShortName>DEBT - Contractual Obligation Maturities of Long-Term, Fiscal Year Maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9954538 - Disclosure - DEBT - Senior Notes - Narrative (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://atkore.com/role/DEBTSeniorNotesNarrativeDetails</Role>
      <ShortName>DEBT - Senior Notes - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9954539 - Disclosure - DEBT - New Senior Secured Term Loan Facility - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTNewSeniorSecuredTermLoanFacilityNarrativeDetails</Role>
      <ShortName>DEBT - New Senior Secured Term Loan Facility - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>9954540 - Disclosure - DEBT - ABL Credit Facility - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTABLCreditFacilityNarrativeDetails</Role>
      <ShortName>DEBT - ABL Credit Facility - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>9954541 - Disclosure - DEBT - Use of Proceeds - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/DEBTUseofProceedsNarrativeDetails</Role>
      <ShortName>DEBT - Use of Proceeds - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>9954542 - Disclosure - FAIR VALUE MEASUREMENTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>9954543 - Disclosure - FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/FAIRVALUEMEASUREMENTSAssetsandLiabilitiesMeasuredatFairValueDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>9954544 - Disclosure - FAIR VALUE MEASUREMENTS - Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/FAIRVALUEMEASUREMENTSEstimatedFairValueofFinancialInstrumentsNotCarriedatFairValueDetails</Role>
      <ShortName>FAIR VALUE MEASUREMENTS - Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>9954545 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/COMMITMENTSANDCONTINGENCIESDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/COMMITMENTSANDCONTINGENCIES</ParentRole>
      <Position>105</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>9954546 - Disclosure - GUARANTEES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/GUARANTEESDetails</Role>
      <ShortName>GUARANTEES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/GUARANTEES</ParentRole>
      <Position>106</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>9954547 - Disclosure - SEGMENT INFORMATION - Schedule of Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONScheduleofSegmentInformationDetails</Role>
      <ShortName>SEGMENT INFORMATION - Schedule of Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>9954548 - Disclosure - SEGMENT INFORMATION - Reconciliation of Operating Segment Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONReconciliationofOperatingSegmentIncomeDetails</Role>
      <ShortName>SEGMENT INFORMATION - Reconciliation of Operating Segment Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>9954549 - Disclosure - SEGMENT INFORMATION - Schedule of Long-lived Assets and Net Sales By Geography (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONScheduleofLonglivedAssetsandNetSalesByGeographyDetails</Role>
      <ShortName>SEGMENT INFORMATION - Schedule of Long-lived Assets and Net Sales By Geography (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>9954550 - Disclosure - SEGMENT INFORMATION - Schedule of Net Sales From External Customers by Product Category (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONScheduleofNetSalesFromExternalCustomersbyProductCategoryDetails</Role>
      <ShortName>SEGMENT INFORMATION - Schedule of Net Sales From External Customers by Product Category (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>9954551 - Disclosure - SEGMENT INFORMATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SEGMENTINFORMATIONNarrativeDetails</Role>
      <ShortName>SEGMENT INFORMATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>9954552 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONBalanceSheetsDetails</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>9954553 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONBalanceSheetsAdditionalInformationDetails</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>113</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>9954554 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONCondensedStatementsofOperationsDetails</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>114</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>9954555 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONCondensedStatementsofCashFlowsDetails</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>115</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>9954556 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONNarrativeDetails</Role>
      <ShortName>SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>116</Position>
    </Report>
    <Report instance="atkr-20230930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>9954557 - Disclosure - SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails</Role>
      <ShortName>SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS</ParentRole>
      <Position>117</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-K" isDefinitelyFs="true" isUsgaap="true" original="atkr-20230930.htm">atkr-20230930.htm</File>
    <File>atkr-20230930.xsd</File>
    <File>atkr-20230930_cal.xml</File>
    <File>atkr-20230930_def.xml</File>
    <File>atkr-20230930_lab.xml</File>
    <File>atkr-20230930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>atkr-20230930_g1.jpg</File>
    <File>atkr-20230930_g2.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="2">http://fasb.org/srt/2023</BaseTaxonomy>
    <BaseTaxonomy items="1441">http://fasb.org/us-gaap/2023</BaseTaxonomy>
    <BaseTaxonomy items="39">http://xbrl.sec.gov/dei/2023</BaseTaxonomy>
    <BaseTaxonomy items="9">http://xbrl.sec.gov/ecd/2023</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
