3.24.3 html 337 520 1 false 99 0 false 8 false false R1.htm 0000001 - Document - Cover Sheet http://atkore.com/role/Cover Cover Cover 1 false false R2.htm 0000002 - Document - Audit Information Sheet http://atkore.com/role/AuditInformation Audit Information Cover 2 false false R3.htm 9952151 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS Sheet http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFOPERATIONS CONSOLIDATED STATEMENTS OF OPERATIONS Statements 3 false false R4.htm 9952152 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Sheet http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOME CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Statements 4 false false R5.htm 9952153 - Statement - CONSOLIDATED BALANCE SHEETS Sheet http://atkore.com/role/CONSOLIDATEDBALANCESHEETS CONSOLIDATED BALANCE SHEETS Statements 5 false false R6.htm 9952154 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) Sheet http://atkore.com/role/CONSOLIDATEDBALANCESHEETSParenthetical CONSOLIDATED BALANCE SHEETS (Parenthetical) Statements 6 false false R7.htm 9952155 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS Sheet http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFCASHFLOWS CONSOLIDATED STATEMENTS OF CASH FLOWS Statements 7 false false R8.htm 9952156 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Sheet http://atkore.com/role/CONSOLIDATEDSTATEMENTSOFSHAREHOLDERSEQUITY CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Statements 8 false false R9.htm 9952157 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Notes 9 false false R10.htm 9952158 - Disclosure - LEASES Sheet http://atkore.com/role/LEASES LEASES Notes 10 false false R11.htm 9952159 - Disclosure - ACQUISITIONS Sheet http://atkore.com/role/ACQUISITIONS ACQUISITIONS Notes 11 false false R12.htm 9952160 - Disclosure - POSTRETIREMENT BENEFITS Sheet http://atkore.com/role/POSTRETIREMENTBENEFITS POSTRETIREMENT BENEFITS Notes 12 false false R13.htm 9952161 - Disclosure - STOCK INCENTIVE PLAN Sheet http://atkore.com/role/STOCKINCENTIVEPLAN STOCK INCENTIVE PLAN Notes 13 false false R14.htm 9952162 - Disclosure - OTHER (INCOME) AND EXPENSE, NET Sheet http://atkore.com/role/OTHERINCOMEANDEXPENSENET OTHER (INCOME) AND EXPENSE, NET Notes 14 false false R15.htm 9952163 - Disclosure - INCOME TAXES Sheet http://atkore.com/role/INCOMETAXES INCOME TAXES Notes 15 false false R16.htm 9952164 - Disclosure - EARNINGS PER SHARE Sheet http://atkore.com/role/EARNINGSPERSHARE EARNINGS PER SHARE Notes 16 false false R17.htm 9952165 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS Sheet http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS ACCUMULATED OTHER COMPREHENSIVE LOSS Notes 17 false false R18.htm 9952166 - Disclosure - INVENTORIES, NET Sheet http://atkore.com/role/INVENTORIESNET INVENTORIES, NET Notes 18 false false R19.htm 9952167 - Disclosure - PROPERTY, PLANT AND EQUIPMENT Sheet http://atkore.com/role/PROPERTYPLANTANDEQUIPMENT PROPERTY, PLANT AND EQUIPMENT Notes 19 false false R20.htm 9952168 - Disclosure - GOODWILL AND INTANGIBLE ASSETS Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETS GOODWILL AND INTANGIBLE ASSETS Notes 20 false false R21.htm 9952169 - Disclosure - DEBT Sheet http://atkore.com/role/DEBT DEBT Notes 21 false false R22.htm 9952170 - Disclosure - FAIR VALUE MEASUREMENTS Sheet http://atkore.com/role/FAIRVALUEMEASUREMENTS FAIR VALUE MEASUREMENTS Notes 22 false false R23.htm 9952171 - Disclosure - COMMITMENTS AND CONTINGENCIES Sheet http://atkore.com/role/COMMITMENTSANDCONTINGENCIES COMMITMENTS AND CONTINGENCIES Notes 23 false false R24.htm 9952172 - Disclosure - GUARANTEES Sheet http://atkore.com/role/GUARANTEES GUARANTEES Notes 24 false false R25.htm 9952173 - Disclosure - SEGMENT INFORMATION Sheet http://atkore.com/role/SEGMENTINFORMATION SEGMENT INFORMATION Notes 25 false false R26.htm 9952174 - Disclosure - SUBSEQUENT EVENTS Sheet http://atkore.com/role/SUBSEQUENTEVENTS SUBSEQUENT EVENTS Notes 26 false false R27.htm 9952175 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATION SCHEDULE I - CONDENSED FINANCIAL INFORMATION Notes 27 false false R28.htm 9952176 - Disclosure - SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS Sheet http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS Notes 28 false false R29.htm 995410 - Disclosure - Pay vs Performance Disclosure Sheet http://xbrl.sec.gov/ecd/role/PvpDisclosure Pay vs Performance Disclosure Notes 29 false false R30.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 30 false false R31.htm 995447 - Disclosure - Insider Trading Policies and Procedures Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc Insider Trading Policies and Procedures Notes 31 false false R32.htm 9955511 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPolicies BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies) Policies 32 false false R33.htm 9955512 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESTables BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) Tables http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIES 33 false false R34.htm 9955513 - Disclosure - LEASES (Tables) Sheet http://atkore.com/role/LEASESTables LEASES (Tables) Tables http://atkore.com/role/LEASES 34 false false R35.htm 9955514 - Disclosure - ACQUISITIONS (Tables) Sheet http://atkore.com/role/ACQUISITIONSTables ACQUISITIONS (Tables) Tables http://atkore.com/role/ACQUISITIONS 35 false false R36.htm 9955515 - Disclosure - POSTRETIREMENT BENEFITS (Tables) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSTables POSTRETIREMENT BENEFITS (Tables) Tables http://atkore.com/role/POSTRETIREMENTBENEFITS 36 false false R37.htm 9955516 - Disclosure - STOCK INCENTIVE PLAN (Tables) Sheet http://atkore.com/role/STOCKINCENTIVEPLANTables STOCK INCENTIVE PLAN (Tables) Tables http://atkore.com/role/STOCKINCENTIVEPLAN 37 false false R38.htm 9955517 - Disclosure - OTHER (INCOME) AND EXPENSE, NET (Tables) Sheet http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables OTHER (INCOME) AND EXPENSE, NET (Tables) Tables http://atkore.com/role/OTHERINCOMEANDEXPENSENET 38 false false R39.htm 9955518 - Disclosure - INCOME TAXES (Tables) Sheet http://atkore.com/role/INCOMETAXESTables INCOME TAXES (Tables) Tables http://atkore.com/role/INCOMETAXES 39 false false R40.htm 9955519 - Disclosure - EARNINGS PER SHARE (Tables) Sheet http://atkore.com/role/EARNINGSPERSHARETables EARNINGS PER SHARE (Tables) Tables http://atkore.com/role/EARNINGSPERSHARE 40 false false R41.htm 9955520 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables) Sheet http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSTables ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables) Tables http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSS 41 false false R42.htm 9955521 - Disclosure - INVENTORIES, NET (Tables) Sheet http://atkore.com/role/INVENTORIESNETTables INVENTORIES, NET (Tables) Tables http://atkore.com/role/INVENTORIESNET 42 false false R43.htm 9955522 - Disclosure - PROPERTY, PLANT AND EQUIPMENT (Tables) Sheet http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTTables PROPERTY, PLANT AND EQUIPMENT (Tables) Tables http://atkore.com/role/PROPERTYPLANTANDEQUIPMENT 43 false false R44.htm 9955523 - Disclosure - GOODWILL AND INTANGIBLE ASSETS (Tables) Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSTables GOODWILL AND INTANGIBLE ASSETS (Tables) Tables http://atkore.com/role/GOODWILLANDINTANGIBLEASSETS 44 false false R45.htm 9955524 - Disclosure - DEBT (Tables) Sheet http://atkore.com/role/DEBTTables DEBT (Tables) Tables http://atkore.com/role/DEBT 45 false false R46.htm 9955525 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) Sheet http://atkore.com/role/FAIRVALUEMEASUREMENTSTables FAIR VALUE MEASUREMENTS (Tables) Tables http://atkore.com/role/FAIRVALUEMEASUREMENTS 46 false false R47.htm 9955526 - Disclosure - SEGMENT INFORMATION (Tables) Sheet http://atkore.com/role/SEGMENTINFORMATIONTables SEGMENT INFORMATION (Tables) Tables http://atkore.com/role/SEGMENTINFORMATION 47 false false R48.htm 9955527 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Share Repurchase Program (Details) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESShareRepurchaseProgramDetails BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Share Repurchase Program (Details) Details 48 false false R49.htm 9955528 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESRevenueRecognitionDetails BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details) Details 49 false false R50.htm 9955529 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESPropertyPlantandEquipmentDetails BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment (Details) Details 50 false false R51.htm 9955530 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Long-Lived Asset and Finite-Lived Intangible Asset Impairments (Details) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESLongLivedAssetandFiniteLivedIntangibleAssetImpairmentsDetails BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Long-Lived Asset and Finite-Lived Intangible Asset Impairments (Details) Details 51 false false R52.htm 9955531 - Disclosure - BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Indefinite-Lived Intangible Asset Impairments (Details) Sheet http://atkore.com/role/BASISOFPRESENTATIONANDSUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESGoodwillandIndefiniteLivedIntangibleAssetImpairmentsDetails BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Indefinite-Lived Intangible Asset Impairments (Details) Details 52 false false R53.htm 9955532 - Disclosure - LEASES - Assets and Liabilities (Details) Sheet http://atkore.com/role/LEASESAssetsandLiabilitiesDetails LEASES - Assets and Liabilities (Details) Details 53 false false R54.htm 9955533 - Disclosure - LEASES - Additional Information (Details) Sheet http://atkore.com/role/LEASESAdditionalInformationDetails LEASES - Additional Information (Details) Details 54 false false R55.htm 9955534 - Disclosure - LEASES - Lease Cost (Details) Sheet http://atkore.com/role/LEASESLeaseCostDetails LEASES - Lease Cost (Details) Details 55 false false R56.htm 9955535 - Disclosure - LEASES - Maturity of Lease Liabilities (Details) Sheet http://atkore.com/role/LEASESMaturityofLeaseLiabilitiesDetails LEASES - Maturity of Lease Liabilities (Details) Details 56 false false R57.htm 9955536 - Disclosure - LEASES - Lease Term and Discount Rate (Details) Sheet http://atkore.com/role/LEASESLeaseTermandDiscountRateDetails LEASES - Lease Term and Discount Rate (Details) Details 57 false false R58.htm 9955537 - Disclosure - ACQUISITIONS - Narrative (Details) Sheet http://atkore.com/role/ACQUISITIONSNarrativeDetails ACQUISITIONS - Narrative (Details) Details 58 false false R59.htm 9955538 - Disclosure - ACQUISITIONS - Summary of Level 3 Fair Values Assigned to Net Assets Acquired and Liabilities Assumed As of Acquisition Date (Details) Sheet http://atkore.com/role/ACQUISITIONSSummaryofLevel3FairValuesAssignedtoNetAssetsAcquiredandLiabilitiesAssumedAsofAcquisitionDateDetails ACQUISITIONS - Summary of Level 3 Fair Values Assigned to Net Assets Acquired and Liabilities Assumed As of Acquisition Date (Details) Details 59 false false R60.htm 9955539 - Disclosure - ACQUISITIONS - Summary of Fair Value as of Acquisition Date (Details) Sheet http://atkore.com/role/ACQUISITIONSSummaryofFairValueasofAcquisitionDateDetails ACQUISITIONS - Summary of Fair Value as of Acquisition Date (Details) Details 60 false false R61.htm 9955540 - Disclosure - ACQUISITIONS - Pro Forma Results (Details) Sheet http://atkore.com/role/ACQUISITIONSProFormaResultsDetails ACQUISITIONS - Pro Forma Results (Details) Details 61 false false R62.htm 9955541 - Disclosure - POSTRETIREMENT BENEFITS - Net Periodic Benefit Cost (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSNetPeriodicBenefitCostDetails POSTRETIREMENT BENEFITS - Net Periodic Benefit Cost (Details) Details 62 false false R63.htm 9955542 - Disclosure - POSTRETIREMENT BENEFITS - Change in Benefit Obligations (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSChangeinBenefitObligationsDetails POSTRETIREMENT BENEFITS - Change in Benefit Obligations (Details) Details 63 false false R64.htm 9955543 - Disclosure - POSTRETIREMENT BENEFITS - Benefit Obligation In Excess Of Plan Assets (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSBenefitObligationInExcessOfPlanAssetsDetails POSTRETIREMENT BENEFITS - Benefit Obligation In Excess Of Plan Assets (Details) Details 64 false false R65.htm 9955544 - Disclosure - POSTRETIREMENT BENEFITS - Narrative (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSNarrativeDetails POSTRETIREMENT BENEFITS - Narrative (Details) Details 65 false false R66.htm 9955545 - Disclosure - POSTRETIREMENT BENEFITS - Weighted-Average Asset Allocations (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSWeightedAverageAssetAllocationsDetails POSTRETIREMENT BENEFITS - Weighted-Average Asset Allocations (Details) Details 66 false false R67.htm 9955546 - Disclosure - POSTRETIREMENT BENEFITS - Asset Allocations by Fair Value Hierarchy (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSAssetAllocationsbyFairValueHierarchyDetails POSTRETIREMENT BENEFITS - Asset Allocations by Fair Value Hierarchy (Details) Details 67 false false R68.htm 9955547 - Disclosure - POSTRETIREMENT BENEFITS - Future Expected Benefit Payments (Details) Sheet http://atkore.com/role/POSTRETIREMENTBENEFITSFutureExpectedBenefitPaymentsDetails POSTRETIREMENT BENEFITS - Future Expected Benefit Payments (Details) Details 68 false false R69.htm 9955548 - Disclosure - STOCK INCENTIVE PLAN - Narrative (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANNarrativeDetails STOCK INCENTIVE PLAN - Narrative (Details) Details 69 false false R70.htm 9955549 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Assumptions (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsAssumptionsDetails STOCK INCENTIVE PLAN - Stock Options Assumptions (Details) Details 70 false false R71.htm 9955550 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Activity (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsActivityDetails STOCK INCENTIVE PLAN - Stock Options Activity (Details) Details 71 false false R72.htm 9955551 - Disclosure - STOCK INCENTIVE PLAN - Stock Options Narrative (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANStockOptionsNarrativeDetails STOCK INCENTIVE PLAN - Stock Options Narrative (Details) Details 72 false false R73.htm 9955552 - Disclosure - STOCK INCENTIVE PLAN - Restricted Stock Narrative (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANRestrictedStockNarrativeDetails STOCK INCENTIVE PLAN - Restricted Stock Narrative (Details) Details 73 false false R74.htm 9955553 - Disclosure - STOCK INCENTIVE PLAN - Schedule of Nonvested Restricted Stock (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANScheduleofNonvestedRestrictedStockDetails STOCK INCENTIVE PLAN - Schedule of Nonvested Restricted Stock (Details) Details 74 false false R75.htm 9955554 - Disclosure - STOCK INCENTIVE PLAN - Performance Share Units Narrative (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANPerformanceShareUnitsNarrativeDetails STOCK INCENTIVE PLAN - Performance Share Units Narrative (Details) Details 75 false false R76.htm 9955555 - Disclosure - STOCK INCENTIVE PLAN - Performance Share Assumptions (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANPerformanceShareAssumptionsDetails STOCK INCENTIVE PLAN - Performance Share Assumptions (Details) Details 76 false false R77.htm 9955556 - Disclosure - STOCK INCENTIVE PLAN - Schedule of Nonvested Performance Shares (Details) Sheet http://atkore.com/role/STOCKINCENTIVEPLANScheduleofNonvestedPerformanceSharesDetails STOCK INCENTIVE PLAN - Schedule of Nonvested Performance Shares (Details) Details 77 false false R78.htm 9955557 - Disclosure - OTHER (INCOME) AND EXPENSE, NET (Details) Sheet http://atkore.com/role/OTHERINCOMEANDEXPENSENETDetails OTHER (INCOME) AND EXPENSE, NET (Details) Details http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables 78 false false R79.htm 9955558 - Disclosure - OTHER (INCOME) AND EXPENSE, NET - Narrative (Details) Sheet http://atkore.com/role/OTHERINCOMEANDEXPENSENETNarrativeDetails OTHER (INCOME) AND EXPENSE, NET - Narrative (Details) Details http://atkore.com/role/OTHERINCOMEANDEXPENSENETTables 79 false false R80.htm 9955559 - Disclosure - INCOME TAXES - Components of Income (Loss) from Continuing Operations and Income Tax Expense (Details) Sheet http://atkore.com/role/INCOMETAXESComponentsofIncomeLossfromContinuingOperationsandIncomeTaxExpenseDetails INCOME TAXES - Components of Income (Loss) from Continuing Operations and Income Tax Expense (Details) Details 80 false false R81.htm 9955560 - Disclosure - INCOME TAXES - Differences Between Federal Income Tax Rate and Effective Income Tax Rate (Details) Sheet http://atkore.com/role/INCOMETAXESDifferencesBetweenFederalIncomeTaxRateandEffectiveIncomeTaxRateDetails INCOME TAXES - Differences Between Federal Income Tax Rate and Effective Income Tax Rate (Details) Details 81 false false R82.htm 9955561 - Disclosure - INCOME TAXES - Narrative (Details) Sheet http://atkore.com/role/INCOMETAXESNarrativeDetails INCOME TAXES - Narrative (Details) Details 82 false false R83.htm 9955562 - Disclosure - INCOME TAXES - Components of Net Deferred Income Tax Assets (Details) Sheet http://atkore.com/role/INCOMETAXESComponentsofNetDeferredIncomeTaxAssetsDetails INCOME TAXES - Components of Net Deferred Income Tax Assets (Details) Details 83 false false R84.htm 9955563 - Disclosure - INCOME TAXES - Unrecognized Tax Benefits (Details) Sheet http://atkore.com/role/INCOMETAXESUnrecognizedTaxBenefitsDetails INCOME TAXES - Unrecognized Tax Benefits (Details) Details 84 false false R85.htm 9955564 - Disclosure - EARNINGS PER SHARE (Details) Sheet http://atkore.com/role/EARNINGSPERSHAREDetails EARNINGS PER SHARE (Details) Details http://atkore.com/role/EARNINGSPERSHARETables 85 false false R86.htm 9955565 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Change in Accumulated Other Comprehensive Loss (Details) Sheet http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSScheduleofChangeinAccumulatedOtherComprehensiveLossDetails ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Change in Accumulated Other Comprehensive Loss (Details) Details 86 false false R87.htm 9955566 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Amounts Reclassified (Details) Sheet http://atkore.com/role/ACCUMULATEDOTHERCOMPREHENSIVELOSSScheduleofAmountsReclassifiedDetails ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Amounts Reclassified (Details) Details 87 false false R88.htm 9955567 - Disclosure - INVENTORIES, NET - Narrative (Details) Sheet http://atkore.com/role/INVENTORIESNETNarrativeDetails INVENTORIES, NET - Narrative (Details) Details 88 false false R89.htm 9955568 - Disclosure - INVENTORIES, NET - Schedule of Company Inventories (Details) Sheet http://atkore.com/role/INVENTORIESNETScheduleofCompanyInventoriesDetails INVENTORIES, NET - Schedule of Company Inventories (Details) Details 89 false false R90.htm 9955569 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) Sheet http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTScheduleofPropertyPlantandEquipmentDetails PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) Details 90 false false R91.htm 9955570 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) Sheet http://atkore.com/role/PROPERTYPLANTANDEQUIPMENTNarrativeDetails PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) Details 91 false false R92.htm 9955571 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSGoodwillDetails GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) Details 92 false false R93.htm 9955572 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSNarrativeDetails GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) Details 93 false false R94.htm 9955573 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSIntangibleAssetsDetails GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) Details 94 false false R95.htm 9955574 - Disclosure - GOODWILL AND INTANGIBLE ASSETS - Expected Amortization Expense (Details) Sheet http://atkore.com/role/GOODWILLANDINTANGIBLEASSETSExpectedAmortizationExpenseDetails GOODWILL AND INTANGIBLE ASSETS - Expected Amortization Expense (Details) Details 95 false false R96.htm 9955575 - Disclosure - DEBT - Schedule of Debt (Details) Sheet http://atkore.com/role/DEBTScheduleofDebtDetails DEBT - Schedule of Debt (Details) Details 96 false false R97.htm 9955576 - Disclosure - DEBT - Contractual Obligation Maturities of Long-Term, Fiscal Year Maturity (Details) Sheet http://atkore.com/role/DEBTContractualObligationMaturitiesofLongTermFiscalYearMaturityDetails DEBT - Contractual Obligation Maturities of Long-Term, Fiscal Year Maturity (Details) Details 97 false false R98.htm 9955577 - Disclosure - DEBT - Senior Notes - Narrative (Details) Notes http://atkore.com/role/DEBTSeniorNotesNarrativeDetails DEBT - Senior Notes - Narrative (Details) Details 98 false false R99.htm 9955578 - Disclosure - DEBT - New Senior Secured Term Loan Facility - Narrative (Details) Sheet http://atkore.com/role/DEBTNewSeniorSecuredTermLoanFacilityNarrativeDetails DEBT - New Senior Secured Term Loan Facility - Narrative (Details) Details 99 false false R100.htm 9955579 - Disclosure - DEBT - ABL Credit Facility - Narrative (Details) Sheet http://atkore.com/role/DEBTABLCreditFacilityNarrativeDetails DEBT - ABL Credit Facility - Narrative (Details) Details 100 false false R101.htm 9955580 - Disclosure - FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) Sheet http://atkore.com/role/FAIRVALUEMEASUREMENTSAssetsandLiabilitiesMeasuredatFairValueDetails FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) Details 101 false false R102.htm 9955581 - Disclosure - FAIR VALUE MEASUREMENTS - Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) Sheet http://atkore.com/role/FAIRVALUEMEASUREMENTSEstimatedFairValueofFinancialInstrumentsNotCarriedatFairValueDetails FAIR VALUE MEASUREMENTS - Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) Details 102 false false R103.htm 9955582 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details) Sheet http://atkore.com/role/COMMITMENTSANDCONTINGENCIESDetails COMMITMENTS AND CONTINGENCIES (Details) Details http://atkore.com/role/COMMITMENTSANDCONTINGENCIES 103 false false R104.htm 9955583 - Disclosure - GUARANTEES (Details) Sheet http://atkore.com/role/GUARANTEESDetails GUARANTEES (Details) Details http://atkore.com/role/GUARANTEES 104 false false R105.htm 9955584 - Disclosure - SEGMENT INFORMATION - Schedule of Segment Information (Details) Sheet http://atkore.com/role/SEGMENTINFORMATIONScheduleofSegmentInformationDetails SEGMENT INFORMATION - Schedule of Segment Information (Details) Details 105 false false R106.htm 9955585 - Disclosure - SEGMENT INFORMATION - Reconciliation of Operating Segment Income (Details) Sheet http://atkore.com/role/SEGMENTINFORMATIONReconciliationofOperatingSegmentIncomeDetails SEGMENT INFORMATION - Reconciliation of Operating Segment Income (Details) Details 106 false false R107.htm 9955586 - Disclosure - SEGMENT INFORMATION - Schedule of Long-lived Assets and Net Sales By Geography (Details) Sheet http://atkore.com/role/SEGMENTINFORMATIONScheduleofLonglivedAssetsandNetSalesByGeographyDetails SEGMENT INFORMATION - Schedule of Long-lived Assets and Net Sales By Geography (Details) Details 107 false false R108.htm 9955587 - Disclosure - SEGMENT INFORMATION - Schedule of Net Sales From External Customers by Product Category (Details) Sheet http://atkore.com/role/SEGMENTINFORMATIONScheduleofNetSalesFromExternalCustomersbyProductCategoryDetails SEGMENT INFORMATION - Schedule of Net Sales From External Customers by Product Category (Details) Details 108 false false R109.htm 9955588 - Disclosure - SEGMENT INFORMATION - Narrative (Details) Sheet http://atkore.com/role/SEGMENTINFORMATIONNarrativeDetails SEGMENT INFORMATION - Narrative (Details) Details 109 false false R110.htm 9955589 - Disclosure - SUBSEQUENT EVENTS (Details) Sheet http://atkore.com/role/SUBSEQUENTEVENTSDetails SUBSEQUENT EVENTS (Details) Details http://atkore.com/role/SUBSEQUENTEVENTS 110 false false R111.htm 9955590 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets (Details) Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONBalanceSheetsDetails SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets (Details) Details 111 false false R112.htm 9955591 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets Additional Information (Details) Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONBalanceSheetsAdditionalInformationDetails SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Balance Sheets Additional Information (Details) Details 112 false false R113.htm 9955592 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Operations (Details) Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONCondensedStatementsofOperationsDetails SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Operations (Details) Details 113 false false R114.htm 9955593 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONCondensedStatementsofCashFlowsDetails SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) Details 114 false false R115.htm 9955594 - Disclosure - SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Narrative (Details) Sheet http://atkore.com/role/SCHEDULEICONDENSEDFINANCIALINFORMATIONNarrativeDetails SCHEDULE I - CONDENSED FINANCIAL INFORMATION - Narrative (Details) Details 115 false false R116.htm 9955595 - Disclosure - SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) Sheet http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTSDetails SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) Details http://atkore.com/role/SCHEDULEIIVALUATIONANDQUALIFYINGACCOUNTS 116 false false All Reports Book All Reports atkr-20240930.htm atkr-20240930.xsd atkr-20240930_cal.xml atkr-20240930_def.xml atkr-20240930_lab.xml atkr-20240930_pre.xml atkr-20240930_g1.jpg atkr-20240930_g2.jpg http://fasb.org/srt/2024 http://fasb.org/us-gaap/2024 http://xbrl.sec.gov/dei/2024 http://xbrl.sec.gov/ecd/2024 true true