<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.24.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>382</ContextCount>
  <ElementCount>373</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>91</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>11</UnitCount>
  <MyReports>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMELOSS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS??? EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSEQUITY</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS??? EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Disclosure - ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIES</Role>
      <ShortName>ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Disclosure - GRAIL SPIN-OFF</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/GRAILSPINOFF</Role>
      <ShortName>GRAIL SPIN-OFF</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - REVENUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/REVENUE</Role>
      <ShortName>REVENUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTS</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - DEBT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/DEBT</Role>
      <ShortName>DEBT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - STOCKHOLDERS??? EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITY</Role>
      <ShortName>STOCKHOLDERS??? EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILS</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - LEGAL PROCEEDINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/LEGALPROCEEDINGS</Role>
      <ShortName>LEGAL PROCEEDINGS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INCOMETAXES</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - SEGMENT INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SEGMENTINFORMATION</Role>
      <ShortName>SEGMENT INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.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>17</Position>
    </Report>
    <Report instance="ilmn-20240929.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="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9954471 - Disclosure - ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIESPolicies</Role>
      <ShortName>ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9954472 - Disclosure - ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIESTables</Role>
      <ShortName>ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIES</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9954473 - Disclosure - GRAIL SPIN-OFF (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/GRAILSPINOFFTables</Role>
      <ShortName>GRAIL SPIN-OFF (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/GRAILSPINOFF</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9954474 - Disclosure - REVENUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/REVENUETables</Role>
      <ShortName>REVENUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/REVENUE</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9954475 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSTables</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTS</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9954476 - Disclosure - DEBT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/DEBTTables</Role>
      <ShortName>DEBT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/DEBT</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9954477 - Disclosure - STOCKHOLDERS??? EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYTables</Role>
      <ShortName>STOCKHOLDERS??? EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/STOCKHOLDERSEQUITY</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9954478 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSTables</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILS</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9954479 - Disclosure - SEGMENT INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SEGMENTINFORMATIONTables</Role>
      <ShortName>SEGMENT INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.illumina.com/role/SEGMENTINFORMATION</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9954480 - Disclosure - ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIESNarrativeDetails</Role>
      <ShortName>ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIESTables</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9954481 - Disclosure - ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Calculation of Weighted Average Shares Used to Calculate Basic and Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/ORGANIZATIONANDSIGNIFICANTACCOUNTINGPOLICIESCalculationofWeightedAverageSharesUsedtoCalculateBasicandDilutedNetLossPerShareDetails</Role>
      <ShortName>ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Calculation of Weighted Average Shares Used to Calculate Basic and Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9954482 - Disclosure - GRAIL SPIN-OFF - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/GRAILSPINOFFNarrativeDetails</Role>
      <ShortName>GRAIL SPIN-OFF - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9954483 - Disclosure - GRAIL SPIN-OFF - Assets and Liabilities Included as Part of the Disposal Group (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/GRAILSPINOFFAssetsandLiabilitiesIncludedasPartoftheDisposalGroupDetails</Role>
      <ShortName>GRAIL SPIN-OFF - Assets and Liabilities Included as Part of the Disposal Group (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9954484 - Disclosure - REVENUE - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/REVENUEDisaggregationofRevenueDetails</Role>
      <ShortName>REVENUE - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9954485 - Disclosure - REVENUE - Performance Obligation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/REVENUEPerformanceObligationDetails</Role>
      <ShortName>REVENUE - Performance Obligation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9954486 - Disclosure - REVENUE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/REVENUENarrativeDetails</Role>
      <ShortName>REVENUE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9954487 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSNarrativeDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9954488 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS - Marketable Equity Securities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSMarketableEquitySecuritiesDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS - Marketable Equity Securities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9954489 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS - Other Commitments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSOtherCommitmentsDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS - Other Commitments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9954490 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS - Fair Value Hierarchy of Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSFairValueHierarchyofAssetsandLiabilitiesDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS - Fair Value Hierarchy of Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9954491 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS - Changes in Estimated Fair Value of Acquisition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSChangesinEstimatedFairValueofAcquisitionDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS - Changes in Estimated Fair Value of Acquisition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9954492 - Disclosure - INVESTMENTS AND FAIR VALUE MEASUREMENTS- Contingent Consideration Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INVESTMENTSANDFAIRVALUEMEASUREMENTSContingentConsiderationLiabilitiesDetails</Role>
      <ShortName>INVESTMENTS AND FAIR VALUE MEASUREMENTS- Contingent Consideration Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9954493 - Disclosure - DEBT - Term Debt Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/DEBTTermDebtObligationsDetails</Role>
      <ShortName>DEBT - Term Debt Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9954494 - Disclosure - DEBT - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/DEBTNarrativeDetails</Role>
      <ShortName>DEBT - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9954495 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYNarrativeDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9954496 - Disclosure - STOCKHOLDERS??? EQUITY - Restricted Stock Activity and Related Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYRestrictedStockActivityandRelatedInformationDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Restricted Stock Activity and Related Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9954497 - Disclosure - STOCKHOLDERS??? EQUITY - Stock Option Activity Under all Stock Option Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYStockOptionActivityUnderallStockOptionPlansDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Stock Option Activity Under all Stock Option Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9954498 - Disclosure - STOCKHOLDERS??? EQUITY - Other Liability - Classified Awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYOtherLiabilityClassifiedAwardsDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Other Liability - Classified Awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9954499 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative - Other Liability - Classified Awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYNarrativeOtherLiabilityClassifiedAwardsDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative - Other Liability - Classified Awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9954500 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative - Employee Stock Purchase Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYNarrativeEmployeeStockPurchasePlanDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative - Employee Stock Purchase Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9954501 - Disclosure - STOCKHOLDERS??? EQUITY - Assumptions Used to Estimate the Weighted Average Fair Value Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYAssumptionsUsedtoEstimatetheWeightedAverageFairValuePerShareDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Assumptions Used to Estimate the Weighted Average Fair Value Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9954502 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative - Share Repurchases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYNarrativeShareRepurchasesDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative - Share Repurchases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9954503 - Disclosure - STOCKHOLDERS??? EQUITY - Share Repurchase Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYShareRepurchaseActivityDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Share Repurchase Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9954504 - Disclosure - STOCKHOLDERS??? EQUITY - Share-based Compensation Expense for all Stock Awards (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYSharebasedCompensationExpenseforallStockAwardsDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Share-based Compensation Expense for all Stock Awards (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9954505 - Disclosure - STOCKHOLDERS??? EQUITY - Narrative - Share-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/STOCKHOLDERSEQUITYNarrativeShareBasedCompensationDetails</Role>
      <ShortName>STOCKHOLDERS??? EQUITY - Narrative - Share-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9954506 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Accounts Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSAccountsReceivableDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Accounts Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9954507 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Inventory (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSInventoryDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Inventory (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9954508 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Accrued Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSAccruedLiabilitiesDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Accrued Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9954509 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Changes in Reserve for Product Warranties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSChangesinReserveforProductWarrantiesDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Changes in Reserve for Product Warranties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9954510 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Warranties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSNarrativeWarrantiesDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Warranties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9954511 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Pre-Tax Restructuring Charge (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSPreTaxRestructuringChargeDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Pre-Tax Restructuring Charge (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9954512 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Restructuring (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSNarrativeRestructuringDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Restructuring (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9954513 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Pre-Tax Charges and Total Costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSPreTaxChargesandTotalCostsDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Pre-Tax Charges and Total Costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9954514 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Impairment of Goodwill and Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSNarrativeImpairmentofGoodwillandIntangibleAssetsDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Impairment of Goodwill and Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9954515 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSGoodwillDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9954516 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Finite-Lived Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSFiniteLivedIntangibleAssetsDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Finite-Lived Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9954517 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Estimated Annual Amortization of Finite-lived Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSEstimatedAnnualAmortizationofFinitelivedIntangibleAssetsDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Estimated Annual Amortization of Finite-lived Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9954518 - Disclosure - SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Derivative Financial Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SUPPLEMENTALBALANCESHEETDETAILSNarrativeDerivativeFinancialInstrumentsDetails</Role>
      <ShortName>SUPPLEMENTAL BALANCE SHEET DETAILS - Narrative - Derivative Financial Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9954519 - Disclosure - LEGAL PROCEEDINGS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/LEGALPROCEEDINGSDetails</Role>
      <ShortName>LEGAL PROCEEDINGS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.illumina.com/role/LEGALPROCEEDINGS</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9954520 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/INCOMETAXESDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.illumina.com/role/INCOMETAXES</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="ilmn-20240929.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9954521 - Disclosure - SEGMENT INFORMATION - Operating Performance and Assets by Segment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.illumina.com/role/SEGMENTINFORMATIONOperatingPerformanceandAssetsbySegmentDetails</Role>
      <ShortName>SEGMENT INFORMATION - Operating Performance and Assets by Segment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</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="ilmn-20240929.htm">ilmn-20240929.htm</File>
    <File>ilmn-20240929.xsd</File>
    <File>ilmn-20240929_cal.xml</File>
    <File>ilmn-20240929_def.xml</File>
    <File>ilmn-20240929_lab.xml</File>
    <File>ilmn-20240929_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>ilmn-20240929_g1.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="990">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="4">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
