XML 65 R54.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Commitments and Contingencies (Details Textual) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 USD ($) | Sep. 30, 2017 dealerships
Manufacturer [Line Items] |  |
Proceeds from Legal Settlements | $ | $ 13.2 |
Volkswagen legal claims | $ | $ 14,700.0 |
Volkswagen [Member] |  |
Manufacturer [Line Items] |  |
Number Of Dealerships | dealerships |  | 7
NumberOfInstallmentsReceived [Line Items] |  | 8
TotalNumberOfInstallments |  | 18
Audi [Member] |  |
Manufacturer [Line Items] |  |
Number Of Dealerships | dealerships |  | 3

X
- Definition [Line Items] for Manufacturer [Table] + References No definition available. + Details
Name: | gpi_ManufacturerLineItems
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 installments received + References No definition available. + Details
Name: | gpi_NumberOfInstallmentsReceived
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of installments + References No definition available. + Details
Name: | gpi_TotalNumberOfInstallments
Namespace Prefix: | gpi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Volkswagen legal claims + References No definition available. + Details
Name: | gpi_Volkswagenlegalclaims
Namespace Prefix: | gpi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Cash received for the settlement of litigation during the current period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585 + Details
Name: | us-gaap_ProceedsFromLegalSettlements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | gpi_ManufacturerAxis=gpi_VolkswagenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | gpi_ManufacturerAxis=gpi_AudiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |