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v2.4.1.9

Annual Financial Information (Details Textual) | Dec. 31, 2014
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Business and Organization [Line Items] |
Number of international regions | 2 gpi_Numberofinternationalregions
East [Member] |
Business and Organization [Line Items] |
Number of dealerships | 41 gpi_NumberOfDealerships / us-gaap_StatementGeographicalAxis = gpi_EastMember
West [Member] |
Business and Organization [Line Items] |
Number of dealerships | 75 gpi_NumberOfDealerships / us-gaap_StatementGeographicalAxis = gpi_WestMember
UNITED STATES |
Business and Organization [Line Items] |
Number of States in which Entity Operates | 14 us-gaap_NumberOfStatesInWhichEntityOperates / us-gaap_StatementGeographicalAxis = country_US
UNITED KINGDOM |
Business and Organization [Line Items] |
Number of Towns in which Entity Operates | 16 gpi_NumberOfTownsInWhichEntityOperates / us-gaap_StatementGeographicalAxis = country_GB
Number of dealerships | 17 gpi_NumberOfDealerships / us-gaap_StatementGeographicalAxis = country_GB
BRAZIL |
Business and Organization [Line Items] |
Number of States in which Entity Operates | 3 us-gaap_NumberOfStatesInWhichEntityOperates / us-gaap_StatementGeographicalAxis = country_BR
Number of dealerships | 17 gpi_NumberOfDealerships / us-gaap_StatementGeographicalAxis = country_BR

X
- Details
Name: | gpi_BusinessAndOrganizationLineItems
Namespace Prefix: | gpi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of dealerships. + References No definition available. + Details
Name: | gpi_NumberOfDealerships
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of international regions + References No definition available. + Details
Name: | gpi_Numberofinternationalregions
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Towns in which Entity Operates + References No definition available. + Details
Name: | gpi_NumberOfTownsInWhichEntityOperates
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of states the entity operates in as of the balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_BR
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_GB
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=gpi_EastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=gpi_WestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |