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Acquisitions and Dispositions Acquisitions and Dispositions (Details textuals) (USD $) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014
Business Acquisition [Line Items] |  |
Total assets | $ 4,098,467,000 us-gaap_Assets | 4,141,492,000 us-gaap_Assets
Business Combination, Consideration Transferred |  | 336,600,000 us-gaap_BusinessCombinationConsiderationTransferred1
UNITED STATES |  |
Business Acquisition [Line Items] |  |
Number of Franchises Disposed | 1 gpi_NumberOfFranchisesDisposed / gpi_CountriesAndStatesAxis = country_US |
Number Of Dealerships Acquired | 1 gpi_NumberOfDealershipsAcquired / gpi_CountriesAndStatesAxis = country_US | 7 gpi_NumberOfDealershipsAcquired / gpi_CountriesAndStatesAxis = country_US
Number of franchises awarded |  | 2 gpi_Numberoffranchisesawarded / gpi_CountriesAndStatesAxis = country_US
Business Acquisition Purchase Price Allocation Goodwill | 103,900,000 gpi_BusinessAcquisitionPurchasePriceAllocationGoodwill / gpi_CountriesAndStatesAxis = country_US |
UNITED KINGDOM |  |
Business Acquisition [Line Items] |  |
Number Of Dealerships Acquired |  | 3 gpi_NumberOfDealershipsAcquired / gpi_CountriesAndStatesAxis = country_GB
Business Acquisition Purchase Price Allocation Goodwill | 18,400,000 gpi_BusinessAcquisitionPurchasePriceAllocationGoodwill / gpi_CountriesAndStatesAxis = country_GB |
BRAZIL |  |
Business Acquisition [Line Items] |  |
Number Of Dealerships Acquired |  | 1 gpi_NumberOfDealershipsAcquired / gpi_CountriesAndStatesAxis = country_BR
Number of franchises awarded |  | 1 gpi_Numberoffranchisesawarded / gpi_CountriesAndStatesAxis = country_BR
Business Acquisition Purchase Price Allocation Goodwill | 0 gpi_BusinessAcquisitionPurchasePriceAllocationGoodwill / gpi_CountriesAndStatesAxis = country_BR |
Businesses acquired [Member] |  |
Business Acquisition [Line Items] |  |
Total assets |  | 411,340,000 us-gaap_Assets / us-gaap_BusinessAcquisitionAxis = gpi_BusinessesacquiredMember

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- Definition Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.18) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 12 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 18 -Article 5 + Details
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- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7488404&loc=d3e6927-128479 + Details
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