<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>572</ContextCount>
  <ElementCount>307</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>97</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000001 - Document - Cover</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/Cover</Role>
      <ShortName>Cover</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>9952151 - Statement - Consolidated Balance Sheets (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>Consolidated Balance Sheets (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>9952152 - Statement - Consolidated Statements of Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ConsolidatedStatementsofIncomeUnaudited</Role>
      <ShortName>Consolidated Statements of Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>9952153 - Statement - Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ConsolidatedStatementsofComprehensiveIncomeUnaudited</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>9952154 - Statement - Consolidated Statements of Shareholders' Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ConsolidatedStatementsofShareholdersEquityUnaudited</Role>
      <ShortName>Consolidated Statements of Shareholders' Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>9952155 - Statement - Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ConsolidatedStatementsofCashFlowsUnaudited</Role>
      <ShortName>Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>9952156 - Disclosure - Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/BasisofPresentation</Role>
      <ShortName>Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>9952157 - Disclosure - Description of Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DescriptionofBusiness</Role>
      <ShortName>Description of Business</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>9952158 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>9952159 - Disclosure - Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/FairValueofFinancialInstruments</Role>
      <ShortName>Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>9952160 - Disclosure - Restricted Securities Available for Sale</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableforSale</Role>
      <ShortName>Restricted Securities Available for Sale</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>9952161 - Disclosure - Loans Receivable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivable</Role>
      <ShortName>Loans Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>9952162 - Disclosure - Reinsurance</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/Reinsurance</Role>
      <ShortName>Reinsurance</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>9952163 - Disclosure - Other Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/OtherIncome</Role>
      <ShortName>Other Income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>9952164 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>9952165 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>9952166 - Disclosure - Net Income Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/NetIncomePerShare</Role>
      <ShortName>Net Income Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>9952167 - Disclosure - Stock Repurchases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockRepurchases</Role>
      <ShortName>Stock Repurchases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>9952168 - Disclosure - Stock-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockBasedCompensationPlans</Role>
      <ShortName>Stock-Based Compensation Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>9952169 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>9952170 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/CommitmentsandContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>9952171 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995445 - Disclosure - Insider Trading Arrangements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements</Role>
      <ShortName>Insider Trading Arrangements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>9955511 - Disclosure - Summary of Significant Accounting Policies (Policy)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesPolicy</Role>
      <ShortName>Summary of Significant Accounting Policies (Policy)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPolicies</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>9955512 - Disclosure - Description of Business (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DescriptionofBusinessTables</Role>
      <ShortName>Description of Business (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DescriptionofBusiness</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>9955513 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPolicies</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>9955514 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/FairValueofFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/FairValueofFinancialInstruments</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>9955515 - Disclosure - Restricted Securities Available For Sale (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableForSaleTables</Role>
      <ShortName>Restricted Securities Available For Sale (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableforSale</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>9955516 - Disclosure - Loans Receivable (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableTables</Role>
      <ShortName>Loans Receivable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivable</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>9955517 - Disclosure - Reinsurance (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ReinsuranceTables</Role>
      <ShortName>Reinsurance (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/Reinsurance</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>9955518 - Disclosure - Other Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/OtherIncomeTables</Role>
      <ShortName>Other Income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/OtherIncome</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>9955519 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/Debt</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>9955520 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/IncomeTaxes</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>9955521 - Disclosure - Net Income Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/NetIncomePerShareTables</Role>
      <ShortName>Net Income Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/NetIncomePerShare</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>9955522 - Disclosure - Stock Repurchases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockRepurchasesTables</Role>
      <ShortName>Stock Repurchases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/StockRepurchases</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>9955523 - Disclosure - Stock-Based Compensation Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockBasedCompensationPlansTables</Role>
      <ShortName>Stock-Based Compensation Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/StockBasedCompensationPlans</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>9955526 - Disclosure - Description of Business (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DescriptionofBusinessNarrativeDetails</Role>
      <ShortName>Description of Business (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DescriptionofBusinessTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>9955527 - Disclosure - Description of Business (Percentage of Consumer Loans Assigned with FICO Score of Less Than 650 or No FICO Score) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DescriptionofBusinessPercentageofConsumerLoansAssignedwithFICOScoreofLessThan650orNoFICOScoreDetails</Role>
      <ShortName>Description of Business (Percentage of Consumer Loans Assigned with FICO Score of Less Than 650 or No FICO Score) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DescriptionofBusinessTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>9955528 - Disclosure - Description of Business (Percentage of Consumer Loans Assigned Based on Volumes) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DescriptionofBusinessPercentageofConsumerLoansAssignedBasedonVolumesDetails</Role>
      <ShortName>Description of Business (Percentage of Consumer Loans Assigned Based on Volumes) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DescriptionofBusinessTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>9955529 - Disclosure - Summary of Significant Accounting Policies (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>9955530 - Disclosure - Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesScheduleofCashandCashEquivalentsDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Schedule of Cash and Cash Equivalents) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/SummaryofSignificantAccountingPoliciesTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>9955531 - Disclosure - Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/FairValueofFinancialInstrumentsScheduleofComparisonoftheCarryingValueandEstimatedFairValueofFinancialInstrumentsDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Schedule of Comparison of the Carrying Value and Estimated Fair Value of Financial Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/FairValueofFinancialInstrumentsTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>9955532 - Disclosure - Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/FairValueofFinancialInstrumentsScheduleofAssetsandLiabilitiesMeasuredatFairValueonaRecurringBasisDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Schedule of Assets and Liabilities, Measured at Fair Value on a Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/FairValueofFinancialInstrumentsTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>9955533 - Disclosure - Restricted Securities Available for Sale (Schedule of Restricted Securities Available for Sale) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableforSaleScheduleofRestrictedSecuritiesAvailableforSaleDetails</Role>
      <ShortName>Restricted Securities Available for Sale (Schedule of Restricted Securities Available for Sale) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableForSaleTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>9955534 - Disclosure - Restricted Securities Available for Sale (Schedule of Restricted Securities Available for Sale by Aging Category) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableforSaleScheduleofRestrictedSecuritiesAvailableforSalebyAgingCategoryDetails</Role>
      <ShortName>Restricted Securities Available for Sale (Schedule of Restricted Securities Available for Sale by Aging Category) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableForSaleTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>9955535 - Disclosure - Restricted Securities Available for Sale (Schedule of Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableforSaleScheduleofCostandEstimatedFairValuesofDebtSecuritiesbyContractualMaturityDetails</Role>
      <ShortName>Restricted Securities Available for Sale (Schedule of Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/RestrictedSecuritiesAvailableForSaleTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>9955536 - Disclosure - Loans Receivable (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableNarrativeDetails</Role>
      <ShortName>Loans Receivable (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>9955537 - Disclosure - Loans Receivable (Schedule of Loans Receivable) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableScheduleofLoansReceivableDetails</Role>
      <ShortName>Loans Receivable (Schedule of Loans Receivable) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>9955538 - Disclosure - Loans Receivable (Summary of Changes in Loans Receivable and Allowance for Credit Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableSummaryofChangesinLoansReceivableandAllowanceforCreditLossesDetails</Role>
      <ShortName>Loans Receivable (Summary of Changes in Loans Receivable and Allowance for Credit Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>9955539 - Disclosure - Loans Receivable Loans Receivable (Summary of Provision for Credit Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableLoansReceivableSummaryofProvisionforCreditLossesDetails</Role>
      <ShortName>Loans Receivable Loans Receivable (Summary of Provision for Credit Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>9955540 - Disclosure - Loans Receivable (Summary of Information Related to New Consumer Loan Assignments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableSummaryofInformationRelatedtoNewConsumerLoanAssignmentsDetails</Role>
      <ShortName>Loans Receivable (Summary of Information Related to New Consumer Loan Assignments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>9955541 - Disclosure - Loans Receivable Loans Receivable (Summary of Changes in Expected Future Net Cash Flows) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableLoansReceivableSummaryofChangesinExpectedFutureNetCashFlowsDetails</Role>
      <ShortName>Loans Receivable Loans Receivable (Summary of Changes in Expected Future Net Cash Flows) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>9955542 - Disclosure - Loans Receivable (Schedule of Consumer Loans Forecasted Collection Percentage) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableScheduleofConsumerLoansForecastedCollectionPercentageDetails</Role>
      <ShortName>Loans Receivable (Schedule of Consumer Loans Forecasted Collection Percentage) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>9955543 - Disclosure - Loans Receivable Loans Receivable (Summary of Past-Due Status) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableLoansReceivableSummaryofPastDueStatusDetails</Role>
      <ShortName>Loans Receivable Loans Receivable (Summary of Past-Due Status) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>9955544 - Disclosure - Loans Receivable (Write-Offs Segmented by Year of Assignment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/LoansReceivableWriteOffsSegmentedbyYearofAssignmentDetails</Role>
      <ShortName>Loans Receivable (Write-Offs Segmented by Year of Assignment) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/LoansReceivableTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>9955545 - Disclosure - Reinsurance (Summary of Reinsurance Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ReinsuranceSummaryofReinsuranceActivityDetails</Role>
      <ShortName>Reinsurance (Summary of Reinsurance Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/ReinsuranceTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>9955546 - Disclosure - Reinsurance (Schedule of Trust Assets and Reinsurance Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/ReinsuranceScheduleofTrustAssetsandReinsuranceLiabilitiesDetails</Role>
      <ShortName>Reinsurance (Schedule of Trust Assets and Reinsurance Liabilities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/ReinsuranceTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>9955547 - Disclosure - Other income (Schedule of Other Income) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/OtherincomeScheduleofOtherIncomeDetails</Role>
      <ShortName>Other income (Schedule of Other Income) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>9955548 - Disclosure - Other Income (Disaggregation of Revenue) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/OtherIncomeDisaggregationofRevenueDetails</Role>
      <ShortName>Other Income (Disaggregation of Revenue) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/OtherIncomeTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>9955549 - Disclosure - Debt (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtNarrativeDetails</Role>
      <ShortName>Debt (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DebtTables</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>9955550 - Disclosure - Debt (Schedule of Principal Debt Outstanding) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtScheduleofPrincipalDebtOutstandingDetails</Role>
      <ShortName>Debt (Schedule of Principal Debt Outstanding) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DebtTables</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>9955551 - Disclosure - Debt (Schedule of General Information of Financing Transaction) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtScheduleofGeneralInformationofFinancingTransactionDetails</Role>
      <ShortName>Debt (Schedule of General Information of Financing Transaction) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DebtTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>9955552 - Disclosure - Debt (Schedule of Additional Information Related to Debt Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtScheduleofAdditionalInformationRelatedtoDebtInstrumentsDetails</Role>
      <ShortName>Debt (Schedule of Additional Information Related to Debt Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DebtTables</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>9955553 - Disclosure - Debt (Summary of Debt) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/DebtSummaryofDebtDetails</Role>
      <ShortName>Debt (Summary of Debt) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/DebtTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>9955554 - Disclosure - Income Taxes (Schedule of Reconciliation of the U.S. Federal Statutory Rate to Effective Tax Rate) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/IncomeTaxesScheduleofReconciliationoftheUSFederalStatutoryRatetoEffectiveTaxRateDetails</Role>
      <ShortName>Income Taxes (Schedule of Reconciliation of the U.S. Federal Statutory Rate to Effective Tax Rate) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/IncomeTaxesTables</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>9955555 - Disclosure - Net Income Per Share (Computation of Weighted Average Shares Outstanding Basic and Diluted) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/NetIncomePerShareComputationofWeightedAverageSharesOutstandingBasicandDilutedDetails</Role>
      <ShortName>Net Income Per Share (Computation of Weighted Average Shares Outstanding Basic and Diluted) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/NetIncomePerShareTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>9955556 - Disclosure - Net Income Per Share (Schedule of Awards Excluded from the Computation of Diluted Net income Per Share) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/NetIncomePerShareScheduleofAwardsExcludedfromtheComputationofDilutedNetincomePerShareDetails</Role>
      <ShortName>Net Income Per Share (Schedule of Awards Excluded from the Computation of Diluted Net income Per Share) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/NetIncomePerShareTables</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>9955557 - Disclosure - Stock Repurchases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockRepurchasesDetails</Role>
      <ShortName>Stock Repurchases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/StockRepurchasesTables</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>9955558 - Disclosure - Stock-Based Compensation Plans Stock-Based Compensation Plans (Summary Of Restricted Stock Units Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockBasedCompensationPlansStockBasedCompensationPlansSummaryOfRestrictedStockUnitsActivityDetails</Role>
      <ShortName>Stock-Based Compensation Plans Stock-Based Compensation Plans (Summary Of Restricted Stock Units Activity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>9955559 - Disclosure - Stock-Based Compensation Plans (Schedule of Stock Based Compensation Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockBasedCompensationPlansScheduleofStockBasedCompensationExpenseDetails</Role>
      <ShortName>Stock-Based Compensation Plans (Schedule of Stock Based Compensation Expense) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/StockBasedCompensationPlansTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>9955560 - Disclosure - Stock-Based Compensation Plans Stock-Based Compensation Plans (Schedule Of Future Share-Based Compensation Cost) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/StockBasedCompensationPlansStockBasedCompensationPlansScheduleOfFutureShareBasedCompensationCostDetails</Role>
      <ShortName>Stock-Based Compensation Plans Stock-Based Compensation Plans (Schedule Of Future Share-Based Compensation Cost) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>9955562 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/CommitmentsandContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/CommitmentsandContingencies</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="cacc-20260331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>9955563 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.creditacceptance.com/role/SubsequentEventsDetails</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.creditacceptance.com/role/SubsequentEvents</ParentRole>
      <Position>73</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" isDefinitelyFs="true" isUsgaap="true" original="cacc-20260331.htm">cacc-20260331.htm</File>
    <File>cacc-20260331.xsd</File>
    <File>cacc-20260331_cal.xml</File>
    <File>cacc-20260331_def.xml</File>
    <File>cacc-20260331_lab.xml</File>
    <File>cacc-20260331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="1286">http://fasb.org/us-gaap/2026</BaseTaxonomy>
    <BaseTaxonomy items="29">http://xbrl.sec.gov/dei/2026</BaseTaxonomy>
    <BaseTaxonomy items="9">http://xbrl.sec.gov/ecd/2026</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
