XML 50 R34.htm IDEA: XBRL DOCUMENT
v3.20.2

Interim Financial Information - Business (Details) | Sep. 30, 2020 town states state dealership
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Brazil |
Business And Organization [Line Items] |
Number of states in which the entity operates | states | 3
Number of dealerships | 17
U.S. |
Business And Organization [Line Items] |
Number of states in which the entity operates | state | 15
Number of dealerships | 119
U.K. |
Business And Organization [Line Items] |
Number of towns in which the entity operates | town | 33
Number of dealerships | 50

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- Definition Business And Organization [Line Items] + References No definition available. + Details
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Namespace Prefix: | gpi_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- 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

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- 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

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- 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

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=gpi_UnitedStatesSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |