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Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2015 | Mar. 31, 2014
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent |  | $ 8,215 us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax | (10,420)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | (4,032)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent | (41,014)us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent | 4,183 us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent
Other Comprehensive Income (Loss), Tax | (1,180)us-gaap_OtherComprehensiveIncomeLossTax | (1,044)us-gaap_OtherComprehensiveIncomeLossTax
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax | 0 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 0 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax | 30,594 us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | (8,215)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax | (4,546)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax | (780)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax
Changes in the balances of each component of accumulated other comprehensive income |  |
Accumulated Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Foreign Currency Translation, Net of Tax, Beginning Balance | (64,075)us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax | (37,827)us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
Accumulated Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Foreign Currency Translation, Net of Tax, Ending Balance | (94,669)us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax | (29,612)us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
Accumulated Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Interest Rate Swaps, Net of Tax, Beginning Balance | (17,909)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax | (13,850)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax
Accumulated Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Interest Rate Swaps, Net of Tax, Ending Balance | (22,455)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax | (14,630)us-gaap_AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance | (81,984)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax | (51,677)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Other comprehensive income (loss), net of tax | (35,140)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent | 7,435 us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance | (117,124)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax | (44,242)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Floorplan Interest Expense [Member] |  |
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax | 2,708 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax / us-gaap_OtherComprehensiveIncomeLocationAxis = gpi_FloorplanInterestExpenseMember | 2,429 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax / us-gaap_OtherComprehensiveIncomeLocationAxis = gpi_FloorplanInterestExpenseMember
Interest Expense [Member] |  |
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, before Tax | 439 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax / us-gaap_OtherComprehensiveIncomeLocationAxis = us-gaap_InterestExpenseMember | 355 us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax / us-gaap_OtherComprehensiveIncomeLocationAxis = us-gaap_InterestExpenseMember
Gain (Loss) on Interest Rate Swaps | Tax effect on other comprehensive income loss before reclassification [Member] |  |
Other Comprehensive Income (Loss), Tax | 3,907 us-gaap_OtherComprehensiveIncomeLossTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember / us-gaap_StatementScenarioAxis = gpi_TaxeffectonothercomprehensiveincomelossbeforereclassificationMember | 1,512 us-gaap_OtherComprehensiveIncomeLossTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember / us-gaap_StatementScenarioAxis = gpi_TaxeffectonothercomprehensiveincomelossbeforereclassificationMember
Total | Tax effect on other comprehensive income loss before reclassification [Member] |  |
Other Comprehensive Income (Loss), Tax | $ 3,907 us-gaap_OtherComprehensiveIncomeLossTax / us-gaap_StatementEquityComponentsAxis = gpi_TotalMember / us-gaap_StatementScenarioAxis = gpi_TaxeffectonothercomprehensiveincomelossbeforereclassificationMember | $ 1,512 us-gaap_OtherComprehensiveIncomeLossTax / us-gaap_StatementEquityComponentsAxis = gpi_TotalMember / us-gaap_StatementScenarioAxis = gpi_TaxeffectonothercomprehensiveincomelossbeforereclassificationMember

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- Definition Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e681-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80784-113994 + Details
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- Definition Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e681-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32022-110900 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 + Details
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- Definition Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e681-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 31 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 + Details
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- Definition Amount before tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32022-110900 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32211-110900 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 35 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6939497&loc=d3e30304-110892 + Details
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