<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>HtmlAndXml</ReportFormat>
  <ContextCount>236</ContextCount>
  <ElementCount>326</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>95</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>11</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <XmlFileName>R1.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1002000 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <XmlFileName>R2.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002501 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <XmlFileName>R3.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003000 - Statement - Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementsOfOperations</Role>
      <ShortName>Consolidated Statements of Operations</ShortName>
      <XmlFileName>R4.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004000 - Statement - Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Consolidated Statements of Comprehensive Income</ShortName>
      <XmlFileName>R5.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004501 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
      <XmlFileName>R6.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - Consolidated Statement of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementOfStockholdersEquity</Role>
      <ShortName>Consolidated Statement of Stockholders' Equity</ShortName>
      <XmlFileName>R7.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005501 - Statement - Consolidated Statement of Stockholders' Equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementOfStockholdersEquityParenthetical</Role>
      <ShortName>Consolidated Statement of Stockholders' Equity (Parenthetical)</ShortName>
      <XmlFileName>R8.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>1006000 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/ConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <XmlFileName>R9.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Interim Financial Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/InterimFinancialInformation</Role>
      <ShortName>Interim Financial Information</ShortName>
      <XmlFileName>R10.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Acquisitions and Dispositions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AcquisitionsAndDispositions</Role>
      <ShortName>Acquisitions and Dispositions</ShortName>
      <XmlFileName>R11.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Derivative Instruments and Risk Management Activities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DerivativeInstrumentsAndRiskManagementActivities</Role>
      <ShortName>Derivative Instruments and Risk Management Activities</ShortName>
      <XmlFileName>R12.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Stock-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/StockBasedCompensationPlans</Role>
      <ShortName>Stock-Based Compensation Plans</ShortName>
      <XmlFileName>R13.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <XmlFileName>R14.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <XmlFileName>R15.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Detail of Certain Balance Sheet Accounts Detail of Certain Balance Sheet Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DetailOfCertainBalanceSheetAccountsDetailOfCertainBalanceSheetAccounts</Role>
      <ShortName>Detail of Certain Balance Sheet Accounts Detail of Certain Balance Sheet Accounts</ShortName>
      <XmlFileName>R16.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - Credit Facilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/CreditFacilities</Role>
      <ShortName>Credit Facilities</ShortName>
      <XmlFileName>R17.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
      <XmlFileName>R18.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <XmlFileName>R19.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <XmlFileName>R20.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - Intangible Franchise Rights and Goodwill</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/IntangibleFranchiseRightsAndGoodwill</Role>
      <ShortName>Intangible Franchise Rights and Goodwill</ShortName>
      <XmlFileName>R21.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Accumulated Other Comprehensive Income</ShortName>
      <XmlFileName>R22.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - Segement Information Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/SegementInformationSegmentInformation</Role>
      <ShortName>Segement Information Segment Information</ShortName>
      <XmlFileName>R23.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2207201 - Disclosure - Interim Financial Information Interim Financial Information (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/InterimFinancialInformationInterimFinancialInformationPolicies</Role>
      <ShortName>Interim Financial Information Interim Financial Information (Policies)</ShortName>
      <XmlFileName>R24.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2307302 - Disclosure - Interim Financial Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/InterimFinancialInformationTables</Role>
      <ShortName>Interim Financial Information (Tables)</ShortName>
      <XmlFileName>R25.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Acquisitions and Dispositions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AcquisitionsAndDispositionsTables</Role>
      <ShortName>Acquisitions and Dispositions (Tables)</ShortName>
      <XmlFileName>R26.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Derivative Instruments and Risk Management Activities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DerivativeInstrumentsAndRiskManagementActivitiesTables</Role>
      <ShortName>Derivative Instruments and Risk Management Activities (Tables)</ShortName>
      <XmlFileName>R27.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Stock-Based Compensation Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/StockBasedCompensationPlansTables</Role>
      <ShortName>Stock-Based Compensation Plans (Tables)</ShortName>
      <XmlFileName>R28.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <XmlFileName>R29.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Detail of Certain Balance Sheet Accounts Detail of Certain Balance Sheet Accounts (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DetailOfCertainBalanceSheetAccountsDetailOfCertainBalanceSheetAccountsTables</Role>
      <ShortName>Detail of Certain Balance Sheet Accounts Detail of Certain Balance Sheet Accounts (Tables)</ShortName>
      <XmlFileName>R30.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Long-Term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebtTables</Role>
      <ShortName>Long-Term Debt (Tables)</ShortName>
      <XmlFileName>R31.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <XmlFileName>R32.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - Intangible Franchise Rights and Goodwill (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/IntangibleFranchiseRightsAndGoodwillTables</Role>
      <ShortName>Intangible Franchise Rights and Goodwill (Tables)</ShortName>
      <XmlFileName>R33.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2319301 - Disclosure - Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AccumulatedOtherComprehensiveIncomeTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Tables)</ShortName>
      <XmlFileName>R34.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2320301 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
      <XmlFileName>R35.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Interim Financial Information (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/InterimFinancialInformationDetailsTextual</Role>
      <ShortName>Interim Financial Information (Details Textual)</ShortName>
      <XmlFileName>R36.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Acquisitions and Dispositions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AcquisitionsAndDispositionsDetails</Role>
      <ShortName>Acquisitions and Dispositions (Details)</ShortName>
      <XmlFileName>R37.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Acquisitions and Dispositions Pro forma Financial Information table (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AcquisitionsAndDispositionsProFormaFinancialInformationTableDetails</Role>
      <ShortName>Acquisitions and Dispositions Pro forma Financial Information table (Details)</ShortName>
      <XmlFileName>R38.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Derivative Instruments and Risk Management Activities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DerivativeInstrumentsAndRiskManagementActivitiesDetails</Role>
      <ShortName>Derivative Instruments and Risk Management Activities (Details)</ShortName>
      <XmlFileName>R39.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Derivative Instruments and Risk Management Activities (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DerivativeInstrumentsAndRiskManagementActivitiesDetailsTextual</Role>
      <ShortName>Derivative Instruments and Risk Management Activities (Details Textual)</ShortName>
      <XmlFileName>R40.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Stock-Based Compensation Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/StockBasedCompensationPlansDetails</Role>
      <ShortName>Stock-Based Compensation Plans (Details)</ShortName>
      <XmlFileName>R41.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Stock-Based Compensation Plans (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/StockBasedCompensationPlansDetailsTextual</Role>
      <ShortName>Stock-Based Compensation Plans (Details Textual)</ShortName>
      <XmlFileName>R42.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <XmlFileName>R43.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Earnings Per Share (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/EarningsPerShareDetailsTextual</Role>
      <ShortName>Earnings Per Share (Details Textual)</ShortName>
      <XmlFileName>R44.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2412401 - Disclosure - Income Taxes (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/IncomeTaxesDetailsTextual</Role>
      <ShortName>Income Taxes (Details Textual)</ShortName>
      <XmlFileName>R45.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Detail of Certain Balance Sheet Accounts (Accounts and Notes Receivable) (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.group1auto.com/role/DetailOfCertainBalanceSheetAccountsAccountsAndNotesReceivableDetails</Role>
      <ShortName>Detail of Certain Balance Sheet Accounts (Accounts and Notes Receivable) (Details)</ShortName>
      <XmlFileName>R46.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Detail of Certain Balance Sheet Accounts (Inventories) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DetailOfCertainBalanceSheetAccountsInventoriesDetails</Role>
      <ShortName>Detail of Certain Balance Sheet Accounts (Inventories) (Details)</ShortName>
      <XmlFileName>R47.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - Detail of Certain Balance Sheet Accounts (Property and Equipment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/DetailOfCertainBalanceSheetAccountsPropertyAndEquipmentDetails</Role>
      <ShortName>Detail of Certain Balance Sheet Accounts (Property and Equipment) (Details)</ShortName>
      <XmlFileName>R48.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2414401 - Disclosure - Credit Facilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/CreditFacilitiesDetails</Role>
      <ShortName>Credit Facilities (Details)</ShortName>
      <XmlFileName>R49.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - Credit Facilities (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/CreditFacilitiesDetailsTextual</Role>
      <ShortName>Credit Facilities (Details Textual)</ShortName>
      <XmlFileName>R50.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Long-Term Debt (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebtDetails</Role>
      <ShortName>Long-Term Debt (Details)</ShortName>
      <XmlFileName>R51.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - Long-Term Debt (Details 1)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebtDetails1</Role>
      <ShortName>Long-Term Debt (Details 1)</ShortName>
      <XmlFileName>R52.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2415404 - Disclosure - Long-Term Debt (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebtDetails2</Role>
      <ShortName>Long-Term Debt (Details 2)</ShortName>
      <XmlFileName>R53.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2415405 - Disclosure - Long-Term Debt (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/LongTermDebtDetailsTextual</Role>
      <ShortName>Long-Term Debt (Details Textual)</ShortName>
      <XmlFileName>R54.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Details)</ShortName>
      <XmlFileName>R55.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2417401 - Disclosure - Commitments and Contingencies (Details Textual)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/CommitmentsAndContingenciesDetailsTextual</Role>
      <ShortName>Commitments and Contingencies (Details Textual)</ShortName>
      <XmlFileName>R56.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2418402 - Disclosure - Intangible Franchise Rights and Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/IntangibleFranchiseRightsAndGoodwillDetails</Role>
      <ShortName>Intangible Franchise Rights and Goodwill (Details)</ShortName>
      <XmlFileName>R57.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2419402 - Disclosure - Accumulated Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/AccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Details)</ShortName>
      <XmlFileName>R58.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2420402 - Disclosure - Segement Information Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.group1auto.com/role/SegementInformationSegmentInformationDetails</Role>
      <ShortName>Segement Information Segment Information (Details)</ShortName>
      <XmlFileName>R59.xml</XmlFileName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element us-gaap_DebtWeightedAverageInterestRate had a mix of decimals attribute values: 0 3.</Log>
    <Log type="Info">Element us-gaap_InterestRateDerivativeAssetsAtFairValue had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_InterestRateDerivativeLiabilitiesAtFairValue had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity had a mix of decimals attribute values: -7 -5.</Log>
    <Log type="Info">Element us-gaap_LongTermDebt had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">'Monetary' elements on report '2408402 - Disclosure - Acquisitions and Dispositions (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2409403 - Disclosure - Derivative Instruments and Risk Management Activities (Details Textual)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Shares' elements on report '2410403 - Disclosure - Stock-Based Compensation Plans (Details Textual)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2410403 - Disclosure - Stock-Based Compensation Plans (Details Textual)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2413404 - Disclosure - Detail of Certain Balance Sheet Accounts (Property and Equipment) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2414402 - Disclosure - Credit Facilities (Details Textual)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2415405 - Disclosure - Long-Term Debt (Details Textual)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2418402 - Disclosure - Intangible Franchise Rights and Goodwill (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2420402 - Disclosure - Segement Information Segment Information (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1002501 - Statement - Consolidated Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Consolidated Statements of Operations</Log>
    <Log type="Info">Process Flow-Through: 1004000 - Statement - Consolidated Statements of Comprehensive Income</Log>
    <Log type="Info">Process Flow-Through: 1004501 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1005501 - Statement - Consolidated Statement of Stockholders' Equity (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1006000 - Statement - Consolidated Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>gpi-20130630.xml</File>
    <File>gpi-20130630.xsd</File>
    <File>gpi-20130630_cal.xml</File>
    <File>gpi-20130630_def.xml</File>
    <File>gpi-20130630_lab.xml</File>
    <File>gpi-20130630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
