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Commitments and Contingencies (Details Textual) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 USD ($) | Mar. 31, 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

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- Definition [Line Items] for Manufacturer [Table] + 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
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Namespace Prefix: | gpi_
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- 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

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- 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=56944662&loc=d3e3536-108585 + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |