<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>383</ContextCount>
  <ElementCount>327</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>76</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>7</UnitCount>
  <MyReports>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>75000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>75010 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>75020 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>75030 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>75040 - Statement - Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_StatementConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>75050 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>75060 - Statement - Consolidated Statements of Cash Flows (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlowsParenthetical</Role>
      <ShortName>Consolidated Statements of Cash Flows (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>995410 - Disclosure - Pay vs Performance Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/PvpDisclosure</Role>
      <ShortName>Pay vs Performance Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.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>9</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995455 - Disclosure - Nature of Business</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureNatureOfBusiness</Role>
      <ShortName>Nature of Business</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>995465 - Disclosure - Basis of Presentation and Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSignificantAccountingPolicies</Role>
      <ShortName>Basis of Presentation and Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>995475 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLosses</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>995485 - Disclosure - Restricted Available-for-Sale Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureRestrictedAvailableForSaleInvestments</Role>
      <ShortName>Restricted Available-for-Sale Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>995495 - Disclosure - Variable Interest Entities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureVariableInterestEntities</Role>
      <ShortName>Variable Interest Entities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>995515 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDebt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>995525 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureStockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>995535 - Disclosure - Disclosure About Fair Value of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDisclosureAboutFairValueOfFinancialInstruments</Role>
      <ShortName>Disclosure About Fair Value of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>995545 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>995555 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureEarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>995565 - Disclosure - Share-Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensation</Role>
      <ShortName>Share-Based Compensation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>995575 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>995585 - Disclosure - Segment Reporting</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSegmentReporting</Role>
      <ShortName>Segment Reporting</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>995595 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>995605 - Disclosure - Basis of Presentation and Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Basis of Presentation and Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSignificantAccountingPolicies</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>995615 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesTables</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLosses</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>995625 - Disclosure - Restricted Available-for-Sale Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureRestrictedAvailableForSaleInvestmentsTables</Role>
      <ShortName>Restricted Available-for-Sale Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureRestrictedAvailableForSaleInvestments</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>995635 - Disclosure - Variable Interest Entities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureVariableInterestEntitiesTables</Role>
      <ShortName>Variable Interest Entities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureVariableInterestEntities</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>995655 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDebt</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>995665 - Disclosure - Stockholders' Equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureStockholdersEquityTables</Role>
      <ShortName>Stockholders' Equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureStockholdersEquity</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>995675 - Disclosure - Disclosure About Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDisclosureAboutFairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Disclosure About Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDisclosureAboutFairValueOfFinancialInstruments</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>995685 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureIncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureIncomeTaxes</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>995695 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureEarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureEarningsPerShare</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>995705 - Disclosure - Share-Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationTables</Role>
      <ShortName>Share-Based Compensation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensation</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>995715 - Disclosure - Segment Reporting (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSegmentReportingTables</Role>
      <ShortName>Segment Reporting (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSegmentReporting</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>995725 - Disclosure - Nature of Business - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureNatureOfBusinessAdditionalInformationDetail</Role>
      <ShortName>Nature of Business - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>995735 - Disclosure - Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureBasisOfPresentationAndSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>995745 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Finance Receivables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfFinanceReceivablesDetail</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Finance Receivables (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>995755 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesAdditionalInformationDetail</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>995765 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financing Receivable Credit Quality Indicators (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfFinancingReceivableCreditQualityIndicatorsDetail</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financing Receivable Credit Quality Indicators (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>995775 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Credit Losses by Product and Origination Year (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfCreditLossesByProductAndOriginationYearDetails</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Credit Losses by Product and Origination Year (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>995785 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Amortized Cost Basis in Past-Due Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesAmortizedCostBasisInPastDueLoansDetail</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Amortized Cost Basis in Past-Due Loans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>995795 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Reconciliation of Allowance for Credit Losses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesReconciliationOfAllowanceForCreditLossesDetail</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Reconciliation of Allowance for Credit Losses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>995805 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Modification Made to Borrowers Experiencing Financial Difficulty (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfModificationMadeToBorrowersExperiencingFinancialDif</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Modification Made to Borrowers Experiencing Financial Difficulty (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>995815 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financial Effects of Borrowers Experiencing Financial Difficulty (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfFinancialEffectsOfBorrowersExperiencingFinancialDif</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Financial Effects of Borrowers Experiencing Financial Difficulty (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>995825 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Amortized Cost Basis for Modifications Made to Borrowers Experiencing Financial Difficulty Subsequently Defaulted (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfAmortizedCostBasisForModificationsMadeToBorrowers</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Amortized Cost Basis for Modifications Made to Borrowers Experiencing Financial Difficulty Subsequently Defaulted (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>995835 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Contractual Delinquencies of Loans that were Modified to Borrowers Experiencing Financial Difficulty (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfContractualDelinquenciesOfLoansThatWereModifiedTo</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Contractual Delinquencies of Loans that were Modified to Borrowers Experiencing Financial Difficulty (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>995845 - Disclosure - Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Contractual Delinquencies of Loans that were Modified to Borrowers Experiencing Financial Difficulty (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureFinanceReceivablesCreditQualityInformationAndAllowanceForCreditLossesSummaryOfContractualDelinquenciesOfLoansThatWereModifiedTo1</Role>
      <ShortName>Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Summary of Contractual Delinquencies of Loans that were Modified to Borrowers Experiencing Financial Difficulty (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>995855 - Disclosure - Restricted Available-for-Sale Investments - Reconciliation of Restricted AFS Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureRestrictedAvailableforsaleInvestmentsReconciliationOfRestrictedAfsInvestmentsDetails</Role>
      <ShortName>Restricted Available-for-Sale Investments - Reconciliation of Restricted AFS Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>995865 - Disclosure - Restricted Available-for-Sale Investments - Summary of Gross Unrealized Losses And Estimated Fair Values of Restricted AFS Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureRestrictedAvailableforsaleInvestmentsSummaryOfGrossUnrealizedLossesAndEstimatedFairValuesOfRestrictedAfsInvestmentsDetails</Role>
      <ShortName>Restricted Available-for-Sale Investments - Summary of Gross Unrealized Losses And Estimated Fair Values of Restricted AFS Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>995875 - Disclosure - Restricted Available-for-Sale Investments - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureRestrictedAvailableForSaleInvestmentsAdditionalInformationDetails</Role>
      <ShortName>Restricted Available-for-Sale Investments - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>995885 - Disclosure - Restricted Available-for-Sale Investments - Summary of Amortized Cost And Estimated Fair Values of Restricted Available-For-Sale Investments by Contractual Maturity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureRestrictedAvailableForSaleInvestmentsSummaryOfAmortizedCostAndEstimatedFairValuesOfRestrictedAvailableForSaleInvestmentsByContractualMaturityDetails</Role>
      <ShortName>Restricted Available-for-Sale Investments - Summary of Amortized Cost And Estimated Fair Values of Restricted Available-For-Sale Investments by Contractual Maturity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>995905 - Disclosure - Variable Interest Entities - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureVariableInterestEntitiesAdditionalInformationDetails</Role>
      <ShortName>Variable Interest Entities - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>995915 - Disclosure - Variable Interest Entities - Summary of Presents the Assets and Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureVariableInterestEntitiesSummaryOfPresentsTheAssetsAndLiabilitiesDetails</Role>
      <ShortName>Variable Interest Entities - Summary of Presents the Assets and Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>995955 - Disclosure - Debt - Summary of the Company's Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDebtSummaryOfCompanySDebtDetail</Role>
      <ShortName>Debt - Summary of the Company's Debt (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>995965 - Disclosure - Debt - Summary of the Company's Debt (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfTheCompanysDebtParentheticalDetail</Role>
      <ShortName>Debt - Summary of the Company's Debt (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>995975 - Disclosure - Debt - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDebtAdditionalInformationDetail</Role>
      <ShortName>Debt - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>995985 - Disclosure - Debt - Summary of Company's Revolving Credit Facilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfCompanysRevolvingCreditFacilitiesDetails</Role>
      <ShortName>Debt - Summary of Company's Revolving Credit Facilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>995995 - Disclosure - Debt - Summary of Company's Revolving Credit Facilities (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfCompanysRevolvingCreditFacilitiesParentheticalDetails</Role>
      <ShortName>Debt - Summary of Company's Revolving Credit Facilities (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>996005 - Disclosure - Debt - Summary Of Borrowings Under The Revolving Credit Facilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfBorrowingsUnderTheRevolvingCreditFacilitiesDetails</Role>
      <ShortName>Debt - Summary Of Borrowings Under The Revolving Credit Facilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>996015 - Disclosure - Debt - Summary Of Borrowings Under The Revolving Credit Facilities (Parenthetical) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfBorrowingsUnderTheRevolvingCreditFacilitiesParentheticalDetails</Role>
      <ShortName>Debt - Summary Of Borrowings Under The Revolving Credit Facilities (Parenthetical) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>996025 - Disclosure - Debt - Summary Of Company's securitizations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureDebtSummaryOfCompanysSecuritizationsDetails</Role>
      <ShortName>Debt - Summary Of Company's securitizations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>996045 - Disclosure - Stockholders' Equity - Additional information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureStockholdersEquityAdditionalInformationDetail</Role>
      <ShortName>Stockholders' Equity - Additional information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>996055 - Disclosure - Stockholders' Equity - Schedule of Dividends Declared Per Share of Common Stock (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureStockholdersEquityScheduleOfDividendsDeclaredPerShareOfCommonStockDetail</Role>
      <ShortName>Stockholders' Equity - Schedule of Dividends Declared Per Share of Common Stock (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>996075 - Disclosure - Disclosure About Fair Value of Financial Instruments - Carrying Amount and Estimated Fair Values of Company's Financial Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureDisclosureAboutFairValueOfFinancialInstrumentsCarryingAmountAndEstimatedFairValuesOfCompanySFinancialInstrumentsDetail</Role>
      <ShortName>Disclosure About Fair Value of Financial Instruments - Carrying Amount and Estimated Fair Values of Company's Financial Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>996085 - Disclosure - Income Taxes - Schedule of Components of Income Taxes (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureIncomeTaxesScheduleOfComponentsOfIncomeTaxesDetail</Role>
      <ShortName>Income Taxes - Schedule of Components of Income Taxes (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>996095 - Disclosure - Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerShareDetail</Role>
      <ShortName>Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>996105 - Disclosure - Earnings Per Share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureEarningsPerShareAdditionalInformationDetail</Role>
      <ShortName>Earnings Per Share - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>996115 - Disclosure - Share-based Compensation - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationAdditionalInformationDetail</Role>
      <ShortName>Share-based Compensation - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>996125 - Disclosure - Share-based Compensation - Summary of Company's Stock Option Plan Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfCompanySStockOptionPlanActivityDetail</Role>
      <ShortName>Share-based Compensation - Summary of Company's Stock Option Plan Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>996135 - Disclosure - Share-based Compensation - Summary of Additional Stock Option Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfAdditionalStockOptionInformationDetail</Role>
      <ShortName>Share-based Compensation - Summary of Additional Stock Option Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>70</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>996145 - Disclosure - Share-based Compensation - Summary of Award Grant Fair Value Assumptions (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSharebasedCompensationSummaryOfAwardGrantFairValueAssumptionsDetail</Role>
      <ShortName>Share-based Compensation - Summary of Award Grant Fair Value Assumptions (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>71</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>996155 - Disclosure - Share-based Compensation - Summary of PRSU Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfPRSUActivityDetail</Role>
      <ShortName>Share-based Compensation - Summary of PRSU Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>996165 - Disclosure - Share-based Compensation - Summary of Additional PRSU Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfAdditionalPRSUInformationDetail</Role>
      <ShortName>Share-based Compensation - Summary of Additional PRSU Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>996175 - Disclosure - Share-based Compensation - Summary of Additional Performance-contingent RSU Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSharebasedCompensationSummaryOfAdditionalPerformancecontingentRsuInformationDetails</Role>
      <ShortName>Share-based Compensation - Summary of Additional Performance-contingent RSU Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>996185 - Disclosure - Share-based Compensation - Summary of Service-based RSU Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSharebasedCompensationSummaryOfServicebasedRsuActivityDetail</Role>
      <ShortName>Share-based Compensation - Summary of Service-based RSU Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>996195 - Disclosure - Share-based Compensation - Summary of Additional Service-based RSU Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSharebasedCompensationSummaryOfAdditionalServicebasedRsuInformationDetail</Role>
      <ShortName>Share-based Compensation - Summary of Additional Service-based RSU Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>996205 - Disclosure - Share-based Compensation - Summary of RSA Activity (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfRSAActivityDetail</Role>
      <ShortName>Share-based Compensation - Summary of RSA Activity (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>996215 - Disclosure - Share-based Compensation - Summary of Additional RSA Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureShareBasedCompensationSummaryOfAdditionalRSAInformationDetail</Role>
      <ShortName>Share-based Compensation - Summary of Additional RSA Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>996225 - Disclosure - Segment Reporting - Additional Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSegmentReportingAdditionalInformationDetails</Role>
      <ShortName>Segment Reporting - Additional Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>996235 - Disclosure - Segment Reporting - Summary of Segment Profit or Loss (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/DisclosureSegmentReportingSummaryOfSegmentProfitOrLossDetails</Role>
      <ShortName>Segment Reporting - Summary of Segment Profit or Loss (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="rm-20250630.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>996245 - Disclosure - Subsequent Events - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.regionalmanagement.com/20250630/taxonomy/role/Role_DisclosureSubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent Events - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</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="rm-20250630.htm">rm-20250630.htm</File>
    <File>rm-20250630.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy items="2">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="1457">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="30">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
    <BaseTaxonomy items="5">http://xbrl.sec.gov/ecd/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
