<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>412</ContextCount>
  <ElementCount>561</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>120</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - Consolidated Statements Of Earnings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedStatementsOfEarnings</Role>
      <ShortName>Consolidated Statements Of Earnings</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - Consolidated Statements Of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements Of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Consolidated Statements Of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements Of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Statement - Consolidated Statements Of Shareholders??? Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/ConsolidatedStatementsOfShareholdersEquity</Role>
      <ShortName>Consolidated Statements Of Shareholders??? Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Statement - Supplemental Cash Flow Information Supplemental Cash Flow (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.carmax.com/role/SupplementalCashFlowInformationSupplementalCashFlowNotes</Role>
      <ShortName>Supplemental Cash Flow Information Supplemental Cash Flow (Notes)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Statement - Supplemental Cash Flow Information Supplemental Cash Flow Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SupplementalCashFlowInformationSupplementalCashFlowInformationTables</Role>
      <ShortName>Supplemental Cash Flow Information Supplemental Cash Flow Information (Tables)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Statement - Supplemental Cash Flow Information Supplemental Cash Flow (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SupplementalCashFlowInformationSupplementalCashFlowDetails</Role>
      <ShortName>Supplemental Cash Flow Information Supplemental Cash Flow (Details)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Summary Of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary Of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Revenue Disclosures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/RevenueDisclosures</Role>
      <ShortName>Revenue Disclosures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - CarMax Auto Finance</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CarMaxAutoFinance</Role>
      <ShortName>CarMax Auto Finance</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Auto Loan Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivables</Role>
      <ShortName>Auto Loan Receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Derivative Instruments And Hedging Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DerivativeInstrumentsAndHedgingActivities</Role>
      <ShortName>Derivative Instruments And Hedging Activities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Property And Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/PropertyAndEquipment</Role>
      <ShortName>Property And Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Intangible Assets, Goodwill and Other</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IntangibleAssetsGoodwillandOther</Role>
      <ShortName>Intangible Assets, Goodwill and Other</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Cancellation Reserves</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CancellationReserves</Role>
      <ShortName>Cancellation Reserves</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Benefit Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlans</Role>
      <ShortName>Benefit Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>9952172 - Disclosure - Stock And Stock-Based Incentive Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlans</Role>
      <ShortName>Stock And Stock-Based Incentive Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9952173 - Disclosure - Net Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/NetEarningsPerShare</Role>
      <ShortName>Net Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9952174 - Disclosure - Accumulated Other Comprehensive Loss</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AccumulatedOtherComprehensiveLoss</Role>
      <ShortName>Accumulated Other Comprehensive Loss</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9952175 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9952176 - Disclosure - Commitments And Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments And Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Summary Of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary Of Significant Accounting Policies (Policy)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.carmax.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Summary Of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary Of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/SummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Revenue Disclosures (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/RevenueDisclosuresTables</Role>
      <ShortName>Revenue Disclosures (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/RevenueDisclosures</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - CarMax Auto Finance (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CarMaxAutoFinanceTables</Role>
      <ShortName>CarMax Auto Finance (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CarMaxAutoFinance</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Auto Loan Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivablesTables</Role>
      <ShortName>Auto Loan Receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AutoLoanReceivables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/FairValueMeasurements</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Property And Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/PropertyAndEquipmentTables</Role>
      <ShortName>Property And Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/PropertyAndEquipment</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Intangible Assets, Goodwill and Other (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IntangibleAssetsGoodwillandOtherTables</Role>
      <ShortName>Intangible Assets, Goodwill and Other (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IntangibleAssetsGoodwillandOther</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Cancellation Reserves (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CancellationReservesTables</Role>
      <ShortName>Cancellation Reserves (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CancellationReserves</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxes</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Benefit Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansTables</Role>
      <ShortName>Benefit Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlans</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/Debt</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955524 - Disclosure - Stock And Stock-Based Incentive Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlans</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955525 - Disclosure - Net Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/NetEarningsPerShareTables</Role>
      <ShortName>Net Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/NetEarningsPerShare</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Accumulated Other Comprehensive Loss (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossTables</Role>
      <ShortName>Accumulated Other Comprehensive Loss (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AccumulatedOtherComprehensiveLoss</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.carmax.com/role/Leases</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Summary Of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Summary Of Significant Accounting Policies (Schedule Of Estimated Useful Lives) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesScheduleOfEstimatedUsefulLivesDetails</Role>
      <ShortName>Summary Of Significant Accounting Policies (Schedule Of Estimated Useful Lives) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/SummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Revenue Disclosures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/RevenueDisclosuresDetails</Role>
      <ShortName>Revenue Disclosures (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/RevenueDisclosuresTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CarMaxAutoFinanceComponentsOfCarMaxAutoFinanceIncomeDetails</Role>
      <ShortName>CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CarMaxAutoFinanceTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Auto Loan Receivables (Auto Loan Receivables, Net) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivablesAutoLoanReceivablesNetDetails</Role>
      <ShortName>Auto Loan Receivables (Auto Loan Receivables, Net) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AutoLoanReceivablesTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Auto Loan Receivables (Ending Managed Receivables By Major Credit Grade) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivablesEndingManagedReceivablesByMajorCreditGradeDetails</Role>
      <ShortName>Auto Loan Receivables (Ending Managed Receivables By Major Credit Grade) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AutoLoanReceivablesTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Auto Loan Receivables (Allowance for Loan Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivablesAllowanceforLoanLossesDetails</Role>
      <ShortName>Auto Loan Receivables (Allowance for Loan Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AutoLoanReceivablesTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Auto Loan Receivables (Past Due Receivables) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AutoLoanReceivablesPastDueReceivablesDetails</Role>
      <ShortName>Auto Loan Receivables (Past Due Receivables) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AutoLoanReceivablesTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Derivative Instruments And Hedging Activities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DerivativeInstrumentsAndHedgingActivitiesNarrativeDetails</Role>
      <ShortName>Derivative Instruments And Hedging Activities (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/DerivativeInstrumentsAndHedgingActivities</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Fair Value Measurements (Schedule Of Items Measured At Fair Value On A Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/FairValueMeasurementsScheduleOfItemsMeasuredAtFairValueOnARecurringBasisDetails</Role>
      <ShortName>Fair Value Measurements (Schedule Of Items Measured At Fair Value On A Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Fair Value Measurements Schedule of Carrying Values and Estimated Fair Values of Debt Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/FairValueMeasurementsScheduleofCarryingValuesandEstimatedFairValuesofDebtInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements Schedule of Carrying Values and Estimated Fair Values of Debt Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Property And Equipment (Schedule Of Property And Equipment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/PropertyAndEquipmentScheduleOfPropertyAndEquipmentDetails</Role>
      <ShortName>Property And Equipment (Schedule Of Property And Equipment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/PropertyAndEquipmentTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Intangible Assets, Goodwill and Other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IntangibleAssetsGoodwillandOtherDetails</Role>
      <ShortName>Intangible Assets, Goodwill and Other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IntangibleAssetsGoodwillandOtherTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Cancellation Reserves (Schedule Of Cancellation Reserves Accrual) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CancellationReservesScheduleOfCancellationReservesAccrualDetails</Role>
      <ShortName>Cancellation Reserves (Schedule Of Cancellation Reserves Accrual) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CancellationReservesTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Cancellation Reserves (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CancellationReservesNarrativeDetails</Role>
      <ShortName>Cancellation Reserves (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CancellationReservesTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Income Taxes (Schedule Of Income Tax Provision) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesScheduleOfIncomeTaxProvisionDetails</Role>
      <ShortName>Income Taxes (Schedule Of Income Tax Provision) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxesTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesScheduleOfEffectiveIncomeTaxRateReconciliationDetails</Role>
      <ShortName>Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxesTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Income Taxes (Schedule Of Temporary Differences Resulting In Deferred Tax Assets And Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesScheduleOfTemporaryDifferencesResultingInDeferredTaxAssetsAndLiabilitiesDetails</Role>
      <ShortName>Income Taxes (Schedule Of Temporary Differences Resulting In Deferred Tax Assets And Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxesTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Income Taxes (Schedule Of Reconciliation Of Unrecognized Tax Benefits) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesScheduleOfReconciliationOfUnrecognizedTaxBenefitsDetails</Role>
      <ShortName>Income Taxes (Schedule Of Reconciliation Of Unrecognized Tax Benefits) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxesTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Income Taxes (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>Income Taxes (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/IncomeTaxesTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Benefit Plans (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansNarrativeDetails</Role>
      <ShortName>Benefit Plans (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Benefit Plans (Benefit Plan Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansBenefitPlanInformationDetails</Role>
      <ShortName>Benefit Plans (Benefit Plan Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Benefit Plans (Components Of Net Pension Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansComponentsOfNetPensionExpenseDetails</Role>
      <ShortName>Benefit Plans (Components Of Net Pension Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Benefit Plans (Assumptions Used To Determine Benefit Obligations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansAssumptionsUsedToDetermineBenefitObligationsDetails</Role>
      <ShortName>Benefit Plans (Assumptions Used To Determine Benefit Obligations) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Benefit Plans (Assumptions Used To Determine Net Pension Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansAssumptionsUsedToDetermineNetPensionExpenseDetails</Role>
      <ShortName>Benefit Plans (Assumptions Used To Determine Net Pension Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Benefit Plans (Schedule Of Fair Value Of Plan Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/BenefitPlansScheduleOfFairValueOfPlanAssetsDetails</Role>
      <ShortName>Benefit Plans (Schedule Of Fair Value Of Plan Assets) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/BenefitPlansTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Debt (Schedule Of Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DebtScheduleOfDebtDetails</Role>
      <ShortName>Debt (Schedule Of Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/DebtTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Debt Debt (Schedule of Maturities of Long-term Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DebtDebtScheduleofMaturitiesofLongtermDebtDetails</Role>
      <ShortName>Debt Debt (Schedule of Maturities of Long-term Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Debt Debt (Schedule of Funding Vehicles) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DebtDebtScheduleofFundingVehiclesDetails</Role>
      <ShortName>Debt Debt (Schedule of Funding Vehicles) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/DebtNarrativeDetails</Role>
      <ShortName>Debt (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/DebtTables</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Stock And Stock-Based Incentive Plans (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansNarrativeDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>9955561 - Disclosure - Stock And Stock-Based Incentive Plans (Schedule Of Common Stoc Repurchases) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansScheduleOfCommonStocRepurchasesDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Schedule Of Common Stoc Repurchases) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Stock And Stock-Based Incentive Plans (Composition Of Share-Based Compensation Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansCompositionOfShareBasedCompensationExpenseDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Composition Of Share-Based Compensation Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Stock And Stock-Based Incentive Plans (Composition Of Share-Based Compensation Expense - By Grant Type) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansCompositionOfShareBasedCompensationExpenseByGrantTypeDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Composition Of Share-Based Compensation Expense - By Grant Type) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>9955564 - Disclosure - Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Unrecognized Compensation Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansStockAndStockBasedIncentivePlansUnrecognizedCompensationExpenseDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Unrecognized Compensation Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>9955565 - Disclosure - Stock And Stock-Based Incentive Plans (Stock Option Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansStockOptionActivityDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Stock Option Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>9955566 - Disclosure - Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Settled) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansStockAndStockBasedIncentivePlansSettledDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Settled) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>9955567 - Disclosure - Stock And Stock-Based Incentive Plans (Assumptions Used To Estimate Option Values) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansAssumptionsUsedToEstimateOptionValuesDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Assumptions Used To Estimate Option Values) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>9955568 - Disclosure - Stock And Stock-Based Incentive Plans (Cash-Settled Restricted Stock Unit Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansCashSettledRestrictedStockUnitActivityDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Cash-Settled Restricted Stock Unit Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>9955569 - Disclosure - Stock And Stock-Based Incentive Plans (Expected Cash Settlement Range Upon Restricted Stock Unit Vesting) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansExpectedCashSettlementRangeUponRestrictedStockUnitVestingDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Expected Cash Settlement Range Upon Restricted Stock Unit Vesting) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>9955570 - Disclosure - Stock And Stock-Based Incentive Plans (Stock-Settled Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansStockSettledActivityDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans (Stock-Settled Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/StockAndStockBasedIncentivePlansTables</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>9955571 - Disclosure - Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Employee Stock Purchase Plan) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/StockAndStockBasedIncentivePlansStockAndStockBasedIncentivePlansEmployeeStockPurchasePlanDetails</Role>
      <ShortName>Stock And Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Employee Stock Purchase Plan) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>9955572 - Disclosure - Net Earnings Per Share (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/NetEarningsPerShareNarrativeDetails</Role>
      <ShortName>Net Earnings Per Share (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/NetEarningsPerShareTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>9955573 - Disclosure - Net Earnings Per Share (Basic And Dilutive Net Earnings Per Share Reconciliations) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/NetEarningsPerShareBasicAndDilutiveNetEarningsPerShareReconciliationsDetails</Role>
      <ShortName>Net Earnings Per Share (Basic And Dilutive Net Earnings Per Share Reconciliations) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/NetEarningsPerShareTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>9955574 - Disclosure - Accumulated Other Comprehensive Loss (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossNarrativeDetails</Role>
      <ShortName>Accumulated Other Comprehensive Loss (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossTables</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>9955575 - Disclosure - Accumulated Other Comprehensive Loss (Accumulated Other Comprehensive Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>Accumulated Other Comprehensive Loss (Accumulated Other Comprehensive Loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossTables</ParentRole>
      <Position>91</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>9955576 - Disclosure - Accumulated Other Comprehensive Loss (Changes In and Reclassifications Out of Accumulated Other Comprehensive Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossChangesInandReclassificationsOutofAccumulatedOtherComprehensiveLossDetails</Role>
      <ShortName>Accumulated Other Comprehensive Loss (Changes In and Reclassifications Out of Accumulated Other Comprehensive Loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/AccumulatedOtherComprehensiveLossTables</ParentRole>
      <Position>92</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>9955577 - Disclosure - Leases (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesNarrativeDetails</Role>
      <ShortName>Leases (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/LeasesTables</ParentRole>
      <Position>93</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>9955578 - Disclosure - Leases Components of Lease Cost (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesComponentsofLeaseCostDetails</Role>
      <ShortName>Leases Components of Lease Cost (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>9955579 - Disclosure - Leases Leases - Supplemental Balance Sheet (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesLeasesSupplementalBalanceSheetDetails</Role>
      <ShortName>Leases Leases - Supplemental Balance Sheet (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>9955580 - Disclosure - Leases Lease Term and Discount Rate (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesLeaseTermandDiscountRateDetails</Role>
      <ShortName>Leases Lease Term and Discount Rate (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>9955581 - Disclosure - Leases Lease Supplemental Cash Flow Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesLeaseSupplementalCashFlowInformationDetails</Role>
      <ShortName>Leases Lease Supplemental Cash Flow Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>9955582 - Disclosure - Leases Maturities of Lease Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/LeasesMaturitiesofLeaseLiabilitiesDetails</Role>
      <ShortName>Leases Maturities of Lease Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="kmx-20260228.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>9955583 - Disclosure - Commitments And Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.carmax.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments And Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.carmax.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>99</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-K" isDefinitelyFs="true" isUsgaap="true" original="kmx-20260228.htm">kmx-20260228.htm</File>
    <File>kmx-20260228.xsd</File>
    <File>kmx-20260228_cal.xml</File>
    <File>kmx-20260228_def.xml</File>
    <File>kmx-20260228_lab.xml</File>
    <File>kmx-20260228_pre.xml</File>
  </InputFiles>
  <SupplementalFiles>
    <File>kmx-20260228_g1.jpg</File>
    <File>kmx-20260228_g2.jpg</File>
    <File>kmx-20260228_g3.jpg</File>
    <File>kmx-20260228_g4.jpg</File>
    <File>kmx-20260228_g5.jpg</File>
    <File>kmx-20260228_g6.jpg</File>
    <File>kmx-20260228_g7.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2025</BaseTaxonomy>
    <BaseTaxonomy items="1552">http://fasb.org/us-gaap/2025</BaseTaxonomy>
    <BaseTaxonomy items="16">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="37">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
