<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>759</ContextCount>
  <ElementCount>514</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>179</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>23</UnitCount>
  <MyReports>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - DOCUMENT AND ENTITY INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/DocumentAndEntityInformation</Role>
      <ShortName>DOCUMENT AND ENTITY INFORMATION</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONSOLIDATED STATEMENTS OF EARNINGS (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedStatementsOfEarningsLoss</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF EARNINGS (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1004000 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedStatementsOfComprehensiveIncomeLoss</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004001 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedStatementsOfComprehensiveIncomeLossParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedStatementsOfChangesInEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1006000 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccountingPolicies</Role>
      <ShortName>ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - CHANGES IN ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ChangesInAccountingPolicies</Role>
      <ShortName>CHANGES IN ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - ACCOUNTING STANDARDS ISSUED BUT NOT YET APPLIED</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccountingStandardsIssuedButNotYetApplied</Role>
      <ShortName>ACCOUNTING STANDARDS ISSUED BUT NOT YET APPLIED</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - CRITICAL ACCOUNTING ESTIMATES AND JUDGEMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CriticalAccountingEstimatesAndJudgements</Role>
      <ShortName>CRITICAL ACCOUNTING ESTIMATES AND JUDGEMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - INVENTORY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/Inventory</Role>
      <ShortName>INVENTORY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - EXPLORATION AND EVALUATION ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ExplorationAndEvaluationAssets</Role>
      <ShortName>EXPLORATION AND EVALUATION ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - PROPERTY, PLANT AND EQUIPMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/PropertyPlantAndEquipment</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssets</Role>
      <ShortName>ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/Investments</Role>
      <ShortName>INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2122100 - Disclosure - OTHER LONG-TERM ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermAssets</Role>
      <ShortName>OTHER LONG-TERM ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2123100 - Disclosure - LONG-TERM DEBT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/LongTermDebt</Role>
      <ShortName>LONG-TERM DEBT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2125100 - Disclosure - OTHER LONG-TERM LIABILITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilities</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2128100 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2131100 - Disclosure - SHARE CAPITAL</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapital</Role>
      <ShortName>SHARE CAPITAL</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2134100 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2137100 - Disclosure - CAPITAL DISCLOSURES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CapitalDisclosures</Role>
      <ShortName>CAPITAL DISCLOSURES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2140100 - Disclosure - NET EARNINGS (LOSS) PER COMMON SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/NetEarningsLossPerCommonShare</Role>
      <ShortName>NET EARNINGS (LOSS) PER COMMON SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2143100 - Disclosure - INTEREST AND OTHER FINANCING EXPENSE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InterestAndOtherFinancingExpense</Role>
      <ShortName>INTEREST AND OTHER FINANCING EXPENSE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2146100 - Disclosure - FINANCIAL INSTRUMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstruments</Role>
      <ShortName>FINANCIAL INSTRUMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2149100 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CommitmentsAndContingencies</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2152100 - Disclosure - SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementalDisclosureOfCashFlowInformation</Role>
      <ShortName>SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2155100 - Disclosure - SEGMENTED INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformation</Role>
      <ShortName>SEGMENTED INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2158100 - Disclosure - REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/RemunerationOfDirectorsAndSeniorManagement</Role>
      <ShortName>REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2159100 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnaudited</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccountingPoliciesPolicies</Role>
      <ShortName>ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - INVENTORY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InventoryTables</Role>
      <ShortName>INVENTORY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/Inventory</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - EXPLORATION AND EVALUATION ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ExplorationAndEvaluationAssetsTables</Role>
      <ShortName>EXPLORATION AND EVALUATION ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/ExplorationAndEvaluationAssets</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - PROPERTY, PLANT AND EQUIPMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/PropertyPlantAndEquipmentTables</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/PropertyPlantAndEquipment</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2319301 - Disclosure - ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssetsTables</Role>
      <ShortName>ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssets</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2320301 - Disclosure - INVESTMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InvestmentsTables</Role>
      <ShortName>INVESTMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/Investments</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2322301 - Disclosure - OTHER LONG-TERM ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermAssetsTables</Role>
      <ShortName>OTHER LONG-TERM ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/OtherLongTermAssets</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2323301 - Disclosure - LONG-TERM DEBT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/LongTermDebtTables</Role>
      <ShortName>LONG-TERM DEBT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/LongTermDebt</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2325301 - Disclosure - OTHER LONG-TERM LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesTables</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/OtherLongTermLiabilities</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2328301 - Disclosure - INCOME TAXES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesTables</Role>
      <ShortName>INCOME TAXES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/IncomeTaxes</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2331301 - Disclosure - SHARE CAPITAL (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapitalTables</Role>
      <ShortName>SHARE CAPITAL (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/ShareCapital</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2334301 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/AccumulatedOtherComprehensiveIncomeLoss</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2337301 - Disclosure - CAPITAL DISCLOSURES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CapitalDisclosuresTables</Role>
      <ShortName>CAPITAL DISCLOSURES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/CapitalDisclosures</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2340301 - Disclosure - NET EARNINGS (LOSS) PER COMMON SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/NetEarningsLossPerCommonShareTables</Role>
      <ShortName>NET EARNINGS (LOSS) PER COMMON SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/NetEarningsLossPerCommonShare</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2343301 - Disclosure - INTEREST AND OTHER FINANCING EXPENSE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InterestAndOtherFinancingExpenseTables</Role>
      <ShortName>INTEREST AND OTHER FINANCING EXPENSE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/InterestAndOtherFinancingExpense</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2346301 - Disclosure - FINANCIAL INSTRUMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsTables</Role>
      <ShortName>FINANCIAL INSTRUMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/FinancialInstruments</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2349301 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2352301 - Disclosure - SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementalDisclosureOfCashFlowInformationTables</Role>
      <ShortName>SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementalDisclosureOfCashFlowInformation</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2355301 - Disclosure - SEGMENTED INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformationTables</Role>
      <ShortName>SEGMENTED INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SegmentedInformation</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2358301 - Disclosure - REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/RemunerationOfDirectorsAndSeniorManagementTables</Role>
      <ShortName>REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/RemunerationOfDirectorsAndSeniorManagement</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2359301 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnaudited</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - ACCOUNTING POLICIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccountingPoliciesNarrativeDetails</Role>
      <ShortName>ACCOUNTING POLICIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2404401 - Disclosure - ACCOUNTING STANDARDS ISSUED BUT NOT YET APPLIED - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccountingStandardsIssuedButNotYetAppliedNarrativeDetails</Role>
      <ShortName>ACCOUNTING STANDARDS ISSUED BUT NOT YET APPLIED - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2407401 - Disclosure - CRITICAL ACCOUNTING ESTIMATES AND JUDGEMENTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CriticalAccountingEstimatesAndJudgementsNarrativeDetails</Role>
      <ShortName>CRITICAL ACCOUNTING ESTIMATES AND JUDGEMENTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - INVENTORY - Schedule of Inventory (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InventoryScheduleOfInventoryDetails</Role>
      <ShortName>INVENTORY - Schedule of Inventory (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - INVENTORY - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InventoryNarrativeDetails</Role>
      <ShortName>INVENTORY - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - EXPLORATION AND EVALUATION ASSETS - Detailed information about exploration and evaluation assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ExplorationAndEvaluationAssetsDetailedInformationAboutExplorationAndEvaluationAssetsDetails</Role>
      <ShortName>EXPLORATION AND EVALUATION ASSETS - Detailed information about exploration and evaluation assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - EXPLORATION AND EVALUATION ASSETS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ExplorationAndEvaluationAssetsNarrativeDetails</Role>
      <ShortName>EXPLORATION AND EVALUATION ASSETS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Detailed information about property, plant and equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/PropertyPlantAndEquipmentDetailedInformationAboutPropertyPlantAndEquipmentDetails</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT - Detailed information about property, plant and equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - PROPERTY, PLANT AND EQUIPMENT - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/PropertyPlantAndEquipmentNarrativeDetails</Role>
      <ShortName>PROPERTY, PLANT AND EQUIPMENT - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2419402 - Disclosure - ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssetsNarrativeDetails</Role>
      <ShortName>ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssetsTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2419403 - Disclosure - ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS - Summary of Net Assets Acquired and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AcquisitionOfInterestsInAthabascaOilSandsProjectAndOtherAssetsSummaryOfNetAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>ACQUISITION OF INTERESTS IN THE ATHABASCA OIL SANDS PROJECT AND OTHER ASSETS - Summary of Net Assets Acquired and Liabilities Assumed (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2420402 - Disclosure - INVESTMENTS - Summary of Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InvestmentsSummaryOfInvestmentsDetails</Role>
      <ShortName>INVESTMENTS - Summary of Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2420403 - Disclosure - INVESTMENTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InvestmentsNarrativeDetails</Role>
      <ShortName>INVESTMENTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2420404 - Disclosure - INVESTMENTS - PrairieSky (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InvestmentsPrairieskyDetails</Role>
      <ShortName>INVESTMENTS - PrairieSky (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2420405 - Disclosure - INVESTMENTS - Inter Pipeline (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InvestmentsInterPipelineDetails</Role>
      <ShortName>INVESTMENTS - Inter Pipeline (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2422402 - Disclosure - OTHER LONG-TERM ASSETS - Schedule of other long-term assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermAssetsScheduleOfOtherLongTermAssetsDetails</Role>
      <ShortName>OTHER LONG-TERM ASSETS - Schedule of other long-term assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2422403 - Disclosure - OTHER LONG-TERM ASSETS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermAssetsNarrativeDetails</Role>
      <ShortName>OTHER LONG-TERM ASSETS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2422404 - Disclosure - OTHER LONG-TERM ASSETS - Summary of Assets, Liabilities, Partners' Equity and Equity (Income) Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermAssetsSummaryOfAssetsLiabilitiesPartnersEquityAndEquityIncomeLossDetails</Role>
      <ShortName>OTHER LONG-TERM ASSETS - Summary of Assets, Liabilities, Partners' Equity and Equity (Income) Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2423402 - Disclosure - LONG-TERM DEBT - Summary of Long-term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/LongTermDebtSummaryOfLongTermDebtDetails</Role>
      <ShortName>LONG-TERM DEBT - Summary of Long-term Debt (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2423403 - Disclosure - LONG-TERM DEBT - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/LongTermDebtNarrativeDetails</Role>
      <ShortName>LONG-TERM DEBT - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2423404 - Disclosure - LONG-TERM DEBT - Schedule of Debt Repayments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/LongTermDebtScheduleOfDebtRepaymentsDetails</Role>
      <ShortName>LONG-TERM DEBT - Schedule of Debt Repayments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2425402 - Disclosure - OTHER LONG-TERM LIABILITIES - Schedule of other long-term liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesScheduleOfOtherLongTermLiabilitiesDetails</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES - Schedule of other long-term liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2425403 - Disclosure - OTHER LONG-TERM LIABILITIES - Asset Retirement Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesAssetRetirementObligationsDetails</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES - Asset Retirement Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2425404 - Disclosure - OTHER LONG-TERM LIABILITIES - Segmented Asset Retirement Obligations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesSegmentedAssetRetirementObligationsDetails</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES - Segmented Asset Retirement Obligations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2425405 - Disclosure - OTHER LONG-TERM LIABILITIES - Share-Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesShareBasedCompensationDetails</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES - Share-Based Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2425406 - Disclosure - OTHER LONG-TERM LIABILITIES - Weighted Average Assumptions Used to Calculate Share-Based Compensation Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/OtherLongTermLiabilitiesWeightedAverageAssumptionsUsedToCalculateShareBasedCompensationLiabilityDetails</Role>
      <ShortName>OTHER LONG-TERM LIABILITIES - Weighted Average Assumptions Used to Calculate Share-Based Compensation Liability (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2428402 - Disclosure - INCOME TAXES - Schedule Of Provision For Income Tax (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesScheduleOfProvisionForIncomeTaxDetails</Role>
      <ShortName>INCOME TAXES - Schedule Of Provision For Income Tax (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2428403 - Disclosure - INCOME TAXES - Schedule of Provision For Income Tax Rate Reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesScheduleOfProvisionForIncomeTaxRateReconciliationDetails</Role>
      <ShortName>INCOME TAXES - Schedule of Provision For Income Tax Rate Reconciliation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2428404 - Disclosure - INCOME TAXES - Summary of Major Temporary Differences (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesSummaryOfMajorTemporaryDifferencesDetails</Role>
      <ShortName>INCOME TAXES - Summary of Major Temporary Differences (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2428405 - Disclosure - INCOME TAXES - Summary of Movements in Deferred Tax Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesSummaryOfMovementsInDeferredTaxAssetsAndLiabilitiesDetails</Role>
      <ShortName>INCOME TAXES - Summary of Movements in Deferred Tax Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2428406 - Disclosure - INCOME TAXES - Summary of Net Deferred Income Tax Liability (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesSummaryOfNetDeferredIncomeTaxLiabilityDetails</Role>
      <ShortName>INCOME TAXES - Summary of Net Deferred Income Tax Liability (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2428407 - Disclosure - INCOME TAXES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>INCOME TAXES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2431402 - Disclosure - SHARE CAPITAL - Outstanding Common Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapitalOutstandingCommonSharesDetails</Role>
      <ShortName>SHARE CAPITAL - Outstanding Common Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2431403 - Disclosure - SHARE CAPITAL - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapitalNarrativeDetails</Role>
      <ShortName>SHARE CAPITAL - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2431404 - Disclosure - SHARE CAPITAL - Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapitalStockOptionActivityDetails</Role>
      <ShortName>SHARE CAPITAL - Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2431405 - Disclosure - SHARE CAPITAL - Range of Exercise Prices of Stock Options (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/ShareCapitalRangeOfExercisePricesOfStockOptionsDetails</Role>
      <ShortName>SHARE CAPITAL - Range of Exercise Prices of Stock Options (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>88</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2434402 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/AccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/AccumulatedOtherComprehensiveIncomeLossTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2437402 - Disclosure - CAPITAL DISCLOSURES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CapitalDisclosuresDetails</Role>
      <ShortName>CAPITAL DISCLOSURES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/CapitalDisclosuresTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2440402 - Disclosure - NET EARNINGS (LOSS) PER COMMON SHARE - Schedule of Basic and Diluted Net Earnings (Loss) per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/NetEarningsLossPerCommonShareScheduleOfBasicAndDilutedNetEarningsLossPerCommonShareDetails</Role>
      <ShortName>NET EARNINGS (LOSS) PER COMMON SHARE - Schedule of Basic and Diluted Net Earnings (Loss) per Common Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/NetEarningsLossPerCommonShareTables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2440403 - Disclosure - NET EARNINGS (LOSS) PER COMMON SHARE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/NetEarningsLossPerCommonShareNarrativeDetails</Role>
      <ShortName>NET EARNINGS (LOSS) PER COMMON SHARE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/NetEarningsLossPerCommonShareTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2443402 - Disclosure - INTEREST AND OTHER FINANCING EXPENSE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/InterestAndOtherFinancingExpenseDetails</Role>
      <ShortName>INTEREST AND OTHER FINANCING EXPENSE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/InterestAndOtherFinancingExpenseTables</ParentRole>
      <Position>93</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2446402 - Disclosure - FINANCIAL INSTRUMENTS - Carrying amounts of financial instruments by category (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsCarryingAmountsOfFinancialInstrumentsByCategoryDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Carrying amounts of financial instruments by category (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2446403 - Disclosure - FINANCIAL INSTRUMENTS - Carrying amounts and fair values of financial instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsCarryingAmountsAndFairValuesOfFinancialInstrumentsDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Carrying amounts and fair values of financial instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2446404 - Disclosure - FINANCIAL INSTRUMENTS - Carrying amounts and reconciliation of derivative financial instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsCarryingAmountsAndReconciliationOfDerivativeFinancialInstrumentsDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Carrying amounts and reconciliation of derivative financial instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2446405 - Disclosure - FINANCIAL INSTRUMENTS - Estimated fair values of derivative financial instruments included in risk management asset (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsEstimatedFairValuesOfDerivativeFinancialInstrumentsIncludedInRiskManagementAssetDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Estimated fair values of derivative financial instruments included in risk management asset (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2446406 - Disclosure - FINANCIAL INSTRUMENTS - Net (gains) losses from risk management activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsNetGainsLossesFromRiskManagementActivitiesDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Net (gains) losses from risk management activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>2446407 - Disclosure - FINANCIAL INSTRUMENTS - Commodity price risk management (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsCommodityPriceRiskManagementDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Commodity price risk management (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>2446408 - Disclosure - FINANCIAL INSTRUMENTS - Foreign currency exchange rate risk management (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsForeignCurrencyExchangeRateRiskManagementDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Foreign currency exchange rate risk management (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>2446409 - Disclosure - FINANCIAL INSTRUMENTS - Financial instrument sensitivities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsFinancialInstrumentSensitivitiesdetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Financial instrument sensitivities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>2446410 - Disclosure - FINANCIAL INSTRUMENTS - Counterparty credit risk management (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsCounterpartyCreditRiskManagementDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Counterparty credit risk management (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>2446411 - Disclosure - FINANCIAL INSTRUMENTS - Maturity dates for financial liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/FinancialInstrumentsMaturityDatesForFinancialLiabilitiesDetails</Role>
      <ShortName>FINANCIAL INSTRUMENTS - Maturity dates for financial liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>2449402 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/CommitmentsAndContingenciesTables</ParentRole>
      <Position>104</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>2452402 - Disclosure - SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION - Supplemental Schedule Of Cash Flow Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementalDisclosureOfCashFlowInformationSupplementalScheduleOfCashFlowInformationDetails</Role>
      <ShortName>SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION - Supplemental Schedule Of Cash Flow Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>105</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>2452403 - Disclosure - SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION - Liabilities Arising From Financing Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementalDisclosureOfCashFlowInformationLiabilitiesArisingFromFinancingActivitiesDetails</Role>
      <ShortName>SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION - Liabilities Arising From Financing Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>106</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>2455402 - Disclosure - SEGMENTED INFORMATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformationNarrativeDetails</Role>
      <ShortName>SEGMENTED INFORMATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>2455403 - Disclosure - SEGMENTED INFORMATION - Operating Segments Earnings (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformationOperatingSegmentsEarningsDetails</Role>
      <ShortName>SEGMENTED INFORMATION - Operating Segments Earnings (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>2455404 - Disclosure - SEGMENTED INFORMATION - Capital Expenditures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformationCapitalExpendituresDetails</Role>
      <ShortName>SEGMENTED INFORMATION - Capital Expenditures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>2455405 - Disclosure - SEGMENTED INFORMATION - Segmented Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SegmentedInformationSegmentedAssetsDetails</Role>
      <ShortName>SEGMENTED INFORMATION - Segmented Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>2458402 - Disclosure - REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/RemunerationOfDirectorsAndSeniorManagementDetails</Role>
      <ShortName>REMUNERATION OF DIRECTORS AND SENIOR MANAGEMENT (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/RemunerationOfDirectorsAndSeniorManagementTables</ParentRole>
      <Position>111</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>2459402 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Twelve Month Average Benchmark Prices (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTwelveMonthAverageBenchmarkPricesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Twelve Month Average Benchmark Prices (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>112</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>2459403 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Proved and Proved Developed Oil and Natural Gas Reserves, Net of Royalties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedProvedAndProvedDevelopedOilAndNaturalGasReservesNetOfRoyaltiesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Proved and Proved Developed Oil and Natural Gas Reserves, Net of Royalties (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>113</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>2459404 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Proved and Proved Developed Natural Gas Reserve Quantities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedProvedAndProvedDevelopedNaturalGasReserveQuantitiesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Proved and Proved Developed Natural Gas Reserve Quantities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>114</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>2459405 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Capitalized Costs Related to Crude Oil and Natural Gas Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedCapitalizedCostsRelatedToCrudeOilAndNaturalGasActivitiesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Capitalized Costs Related to Crude Oil and Natural Gas Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>115</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>2459406 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Costs Incurred in Crude Oil and Natural Gas Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedCostsIncurredInCrudeOilAndNaturalGasActivitiesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Costs Incurred in Crude Oil and Natural Gas Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>116</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>2459407 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Results of Operations from Crude Oil and Natural Gas Producing Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedResultsOfOperationsFromCrudeOilAndNaturalGasProducingActivitiesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Results of Operations from Crude Oil and Natural Gas Producing Activities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>117</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>2459408 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Future Net Cash Flows Relating to Proved Crude Oil and Natural Gas Reserves (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedFutureNetCashFlowsRelatingToProvedCrudeOilAndNaturalGasReservesDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Future Net Cash Flows Relating to Proved Crude Oil and Natural Gas Reserves (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>118</Position>
    </Report>
    <Report instance="cnq-20181231.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>2459409 - Disclosure - SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Sources of Change in the Standardized Measure of Discounted Future Net Cash Flows (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedSourcesOfChangeInStandardizedMeasureOfDiscountedFutureNetCashFlowsDetails</Role>
      <ShortName>SUPPLEMENTARY OIL &amp; GAS INFORMATION (Unaudited) - Sources of Change in the Standardized Measure of Discounted Future Net Cash Flows (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.cnrl.com/role/SupplementaryOilGasInformationUnauditedTables</ParentRole>
      <Position>119</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>cnq-20181231.xml</File>
    <File>cnq-20181231.xsd</File>
    <File>cnq-20181231_cal.xml</File>
    <File>cnq-20181231_def.xml</File>
    <File>cnq-20181231_lab.xml</File>
    <File>cnq-20181231_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.ifrs.org/taxonomy/2018-03-16/ifrs-full</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2018-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/currency/2017-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/invest/2013-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2018-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
