<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>138</ContextCount>
  <ElementCount>172</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>32</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>001 - Statement - Consolidated and Combined Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ConsolidatedIncomeStatement</Role>
      <ShortName>Consolidated and Combined Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>002 - Statement - Consolidated and Combined Statements of Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ConsolidatedComprehensiveIncome</Role>
      <ShortName>Consolidated and Combined Statements of Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>003 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ConsolidatedBalanceSheet</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>004 - Statement - Condensed Consolidated Balance Sheets (Parentheticals)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ConsolidatedBalanceSheet_Parentheticals</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parentheticals)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>005 - Statement - Condensed Consolidated and Combined Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ConsolidatedCashFlow</Role>
      <ShortName>Condensed Consolidated and Combined Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>006 - Statement - Consolidated and Combined Statements of Changes in Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ShareholdersEquityType2or3</Role>
      <ShortName>Consolidated and Combined Statements of Changes in Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>007 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/BasisofPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>008 - Disclosure - Revenue and Accounts Receivable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/RevenueandAccountsReceivable</Role>
      <ShortName>Revenue and Accounts Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>009 - Disclosure - Restructuring and Other Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/RestructuringandOtherActivities</Role>
      <ShortName>Restructuring and Other Activities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>010 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>011 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/LongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>012 - Disclosure - Financial Instruments and Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/FinancialInstrumentsandFairValueMeasurements</Role>
      <ShortName>Financial Instruments and Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>013 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>014 - Disclosure - Segment and Geographic Data</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SegmentandGeographicData</Role>
      <ShortName>Segment and Geographic Data</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>015 - Disclosure - Contingencies and Commitments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ContingenciesandCommitments</Role>
      <ShortName>Contingencies and Commitments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>016 - Disclosure - Basic and Diluted Net Loss Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/BasicandDilutedNetLossPerShare</Role>
      <ShortName>Basic and Diluted Net Loss Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.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>18</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>996000 - Disclosure - Accounting Policies, by Policy (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/AccountingPoliciesByPolicy</Role>
      <ShortName>Accounting Policies, by Policy (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>996001 - Disclosure - Restructuring and Other Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/RestructuringandOtherActivitiesTables</Role>
      <ShortName>Restructuring and Other Activities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/RestructuringandOtherActivities</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>996002 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/Leases</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>996003 - Disclosure - Long-Term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/LongTermDebtTables</Role>
      <ShortName>Long-Term Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/LongTermDebt</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>996004 - Disclosure - Financial Instruments and Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/FinancialInstrumentsandFairValueMeasurementsTables</Role>
      <ShortName>Financial Instruments and Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/FinancialInstrumentsandFairValueMeasurements</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>996005 - Disclosure - Segment and Geographic Data (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SegmentandGeographicDataTables</Role>
      <ShortName>Segment and Geographic Data (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/SegmentandGeographicData</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>996006 - Disclosure - Basic and Diluted Net Loss Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/BasicandDilutedNetLossPerShareTables</Role>
      <ShortName>Basic and Diluted Net Loss Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.magnera.com/role/BasicandDilutedNetLossPerShare</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>996007 - Disclosure - Restructuring and Other Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/RestructuringandOtherActivitiesDetails</Role>
      <ShortName>Restructuring and Other Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.magnera.com/role/RestructuringandOtherActivitiesTables</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>996008 - Disclosure - Restructuring and Other Activities - Charges for Restructuring and Other Activities by Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ChargesforRestructuringandOtherActivitiesbySegmentTable</Role>
      <ShortName>Restructuring and Other Activities - Charges for Restructuring and Other Activities by Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>996009 - Disclosure - Restructuring and Other Activities - Accrual Activity for Restructuring and Other Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/AccrualActivityforRestructuringandOtherActivitiesTable</Role>
      <ShortName>Restructuring and Other Activities - Accrual Activity for Restructuring and Other Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>996010 - Disclosure - Leases - Lease Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/LeaseAssetsandLiabilitiesTable</Role>
      <ShortName>Leases - Lease Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>996011 - Disclosure - Long-Term Debt - Long-Term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/LongTermDebtTable</Role>
      <ShortName>Long-Term Debt - Long-Term Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>996012 - Disclosure - Financial Instruments and Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/FinancialInstrumentsandFairValueMeasurementsDetails</Role>
      <ShortName>Financial Instruments and Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.magnera.com/role/FinancialInstrumentsandFairValueMeasurementsTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>996013 - Disclosure - Financial Instruments and Fair Value Measurements - Fair Value of Derivatives and Location on Consolidated Balance Sheets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/FairValueofDerivativesandLocationonConsolidatedBalanceSheetsTable</Role>
      <ShortName>Financial Instruments and Fair Value Measurements - Fair Value of Derivatives and Location on Consolidated Balance Sheets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>996014 - Disclosure - Financial Instruments and Fair Value Measurements - Effect of Derivatives on Consolidated and Combined Statements of Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/EffectofDerivativesonConsolidatedandCombinedStatementsofOperationsTable</Role>
      <ShortName>Financial Instruments and Fair Value Measurements - Effect of Derivatives on Consolidated and Combined Statements of Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>996015 - Disclosure - Segment and Geographic Data (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SegmentandGeographicDataDetails</Role>
      <ShortName>Segment and Geographic Data (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.magnera.com/role/SegmentandGeographicDataTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>996016 - Disclosure - Segment and Geographic Data - Selected Information by Reportable Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SelectedInformationbyReportableSegmentTable</Role>
      <ShortName>Segment and Geographic Data - Selected Information by Reportable Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>996017 - Disclosure - Segment and Geographic Data - Selected Information by Geographical Region (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SelectedInformationbyGeographicalRegionTable</Role>
      <ShortName>Segment and Geographic Data - Selected Information by Geographical Region (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>996018 - Disclosure - Segment and Geographic Data - Selected Information by Product Line (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/SelectedInformationbyProductLineTable</Role>
      <ShortName>Segment and Geographic Data - Selected Information by Product Line (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>996019 - Disclosure - Contingencies and Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/ContingenciesandCommitmentsDetails</Role>
      <ShortName>Contingencies and Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.magnera.com/role/ContingenciesandCommitments</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>996020 - Disclosure - Basic and Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/BasicandDilutedNetLossPerShareDetails</Role>
      <ShortName>Basic and Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.magnera.com/role/BasicandDilutedNetLossPerShareTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="form10q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>996021 - Disclosure - Basic and Diluted Net Loss Per Share - Basic and Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.magnera.com/role/BasicandDilutedNetLossPerShareTable</Role>
      <ShortName>Basic and Diluted Net Loss Per Share - Basic and Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</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-Q" isDefinitelyFs="true" isUsgaap="true" original="form10q.htm">form10q.htm</File>
    <File>magn-20260627.xsd</File>
    <File>magn-20260627_cal.xml</File>
    <File>magn-20260627_def.xml</File>
    <File>magn-20260627_lab.xml</File>
    <File>magn-20260627_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>image1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="508">http://fasb.org/us-gaap/2026</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2026</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2026</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
