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Segment Information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of Reportable Segments									3us-gaap_NumberOfReportableSegments
Business Combination, Acquisition Related Costs										$ 6,500,000us-gaap_BusinessCombinationAcquisitionRelatedCosts
New vehicle retail sales									5,741,619,000gpi_NewVehicleRetailSales	5,224,921,000gpi_NewVehicleRetailSales	4,291,098,000gpi_NewVehicleRetailSales
Used vehicle retail sales									2,324,868,000gpi_UsedVehicleRetailSales	2,039,428,000gpi_UsedVehicleRetailSales	1,756,918,000gpi_UsedVehicleRetailSales
Used vehicle wholesale sales									379,143,000gpi_UsedVehicleWholesaleSales	332,185,000gpi_UsedVehicleWholesaleSales	288,139,000gpi_UsedVehicleWholesaleSales
Parts and service									1,125,694,000gpi_PartsAndServiceSales	1,010,685,000gpi_PartsAndServiceSales	880,070,000gpi_PartsAndServiceSales
Total revenues	2,538,940,000us-gaap_Revenues	2,626,448,000us-gaap_Revenues	2,511,638,000us-gaap_Revenues	2,260,863,000us-gaap_Revenues	2,279,492,000us-gaap_Revenues	2,340,147,000us-gaap_Revenues	2,335,110,000us-gaap_Revenues	1,963,832,000us-gaap_Revenues	9,937,889,000us-gaap_Revenues	8,918,581,000us-gaap_Revenues	7,476,100,000us-gaap_Revenues
Gross profit	365,959,000us-gaap_GrossProfit	374,709,000us-gaap_GrossProfit	369,148,000us-gaap_GrossProfit	338,122,000us-gaap_GrossProfit	321,321,000us-gaap_GrossProfit	329,462,000us-gaap_GrossProfit	341,274,000us-gaap_GrossProfit	300,489,000us-gaap_GrossProfit	1,447,938,000us-gaap_GrossProfit	1,292,546,000us-gaap_GrossProfit	1,117,252,000us-gaap_GrossProfit
Selling, general and administrative expense (2)									1,061,964,000us-gaap_SellingGeneralAndAdministrativeExpense	976,856,000us-gaap_SellingGeneralAndAdministrativeExpense	848,446,000us-gaap_SellingGeneralAndAdministrativeExpense
Depreciation and amortization expense									42,344,000us-gaap_DepreciationDepletionAndAmortization	35,826,000us-gaap_DepreciationDepletionAndAmortization	31,534,000us-gaap_DepreciationDepletionAndAmortization
Asset Impairment Charge	30,400,000us-gaap_AssetImpairmentCharges	9,400,000us-gaap_AssetImpairmentCharges	1,700,000us-gaap_AssetImpairmentCharges						41,520,000us-gaap_AssetImpairmentCharges	6,542,000us-gaap_AssetImpairmentCharges	7,276,000us-gaap_AssetImpairmentCharges
Floorplan interest expense									(41,614,000)gpi_FloorPlanInterestExpense	(41,667,000)gpi_FloorPlanInterestExpense	(31,796,000)gpi_FloorPlanInterestExpense
Other interest expense, net									(49,693,000)us-gaap_InterestExpenseOther	(38,971,000)us-gaap_InterestExpenseOther	(37,465,000)us-gaap_InterestExpenseOther
Other Expenses									0us-gaap_OtherExpenses	(789,000)us-gaap_OtherExpenses	0us-gaap_OtherExpenses
Gains (Losses) on Extinguishment of Debt									46,403,000us-gaap_GainsLossesOnExtinguishmentOfDebt	0us-gaap_GainsLossesOnExtinguishmentOfDebt	0us-gaap_GainsLossesOnExtinguishmentOfDebt
Income before income taxes									164,400,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	191,895,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	160,735,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Provision for income taxes									71,396,000us-gaap_IncomeTaxExpenseBenefit	77,903,000us-gaap_IncomeTaxExpenseBenefit	60,526,000us-gaap_IncomeTaxExpenseBenefit
Net income									93,004,000us-gaap_NetIncomeLoss	113,992,000us-gaap_NetIncomeLoss	100,209,000us-gaap_NetIncomeLoss
Total assets	4,141,492,000us-gaap_Assets				3,819,478,000us-gaap_Assets				4,141,492,000us-gaap_Assets	3,819,478,000us-gaap_Assets
United States [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights	958,144,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember				828,881,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember				958,144,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	828,881,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
New vehicle retail sales									4,669,512,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	4,220,913,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	4,004,211,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Used vehicle retail sales									1,923,740,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	1,728,072,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	1,623,588,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Used vehicle wholesale sales									279,074,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	236,995,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	240,789,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Parts and service									966,672,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	878,951,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	833,964,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Finance and insurance									336,243,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	288,409,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	251,458,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Total revenues									8,175,241,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	7,353,340,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	6,954,010,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Gross profit									1,245,907,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	1,116,415,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	1,054,270,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Selling, general and administrative expense (2)									891,693,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	830,275,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	796,998,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Depreciation and amortization expense									36,701,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	31,671,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	29,137,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Asset Impairment Charge									15,570,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	6,542,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	7,276,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Floorplan interest expense									(34,060,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	(33,789,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	(30,736,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Other interest expense, net									(46,516,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	(37,982,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	(36,831,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Other Expenses										0us-gaap_OtherExpenses / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Gains (Losses) on Extinguishment of Debt									(46,403,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Income before income taxes									174,964,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	176,156,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	153,292,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Provision for income taxes									(77,715,000)us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	70,815,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	58,794,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Net income									97,249,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	105,340,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	94,498,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Capital expenditures									88,774,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	64,442,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	61,214,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
Total assets	3,529,643,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember				3,241,192,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember				3,529,643,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember	3,241,192,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedStatesMember
United Kingdom [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights	43,295,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember				28,261,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember				43,295,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	28,261,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
New vehicle retail sales									519,137,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	441,537,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	286,887,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Used vehicle retail sales									283,147,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	221,590,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	133,330,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Used vehicle wholesale sales									82,235,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	66,077,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	47,350,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Parts and service									83,747,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	67,557,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	46,106,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Finance and insurance									18,986,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	14,028,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	8,417,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Total revenues									987,252,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	810,789,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	522,090,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Gross profit									115,393,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	93,221,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	62,982,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Selling, general and administrative expense (2)									90,427,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	74,777,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	51,448,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Depreciation and amortization expense									3,403,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	2,573,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	2,397,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Asset Impairment Charge									0us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	0us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	0us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Floorplan interest expense									(1,662,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	(1,589,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	(1,060,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Other interest expense, net									(2,065,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	(1,158,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	(634,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Other Expenses										0us-gaap_OtherExpenses / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Gains (Losses) on Extinguishment of Debt									0us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Income before income taxes									17,836,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	13,124,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	7,443,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Provision for income taxes									(3,561,000)us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	3,064,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	1,732,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Net income									14,275,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	10,061,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	5,711,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Capital expenditures									3,679,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	1,489,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	747,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Total assets	327,644,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember				237,960,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember				327,644,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember	237,960,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_UnitedKingdomMember
Brazil [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights	132,885,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember				181,666,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember				132,885,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	181,666,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
New vehicle retail sales									552,970,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	562,471,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Used vehicle retail sales									117,981,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	89,766,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Used vehicle wholesale sales									17,834,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	29,113,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Parts and service									75,275,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	64,177,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Finance and insurance									11,336,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	8,925,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Total revenues									775,396,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	754,452,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Gross profit									86,638,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	82,910,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Selling, general and administrative expense (2)									79,844,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	71,804,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Depreciation and amortization expense									2,240,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	1,582,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Asset Impairment Charge									25,950,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Floorplan interest expense									(5,892,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	(6,289,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Other interest expense, net									(1,112,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	169,000us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Other Expenses										(789,000)us-gaap_OtherExpenses / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Gains (Losses) on Extinguishment of Debt									0us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Income before income taxes									(28,400,000)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	2,615,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Provision for income taxes									9,880,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	4,024,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Net income									(18,520,000)us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	(1,409,000)us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Capital expenditures									5,256,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	3,285,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	0gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Total assets	284,205,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember				340,326,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember				284,205,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember	340,326,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = gpi_BrazilMember
Consolidated Entities [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights	1,134,324,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember				1,038,808,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember				1,134,324,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	1,038,808,000us-gaap_IntangibleAssetsNetIncludingGoodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
New vehicle retail sales									5,741,619,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	5,224,921,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	4,291,098,000gpi_NewVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Used vehicle retail sales									2,324,868,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	2,039,428,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	1,756,918,000gpi_UsedVehicleRetailSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Used vehicle wholesale sales									379,143,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	332,185,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	288,139,000gpi_UsedVehicleWholesaleSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Parts and service									1,125,694,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	1,010,685,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	880,070,000gpi_PartsAndServiceSales / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Finance and insurance									366,565,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	311,362,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	259,875,000gpi_Financeandinsurancerevenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Total revenues									9,937,889,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	8,918,581,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	7,476,100,000us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Gross profit									1,447,938,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	1,292,546,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	1,117,252,000us-gaap_GrossProfit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Selling, general and administrative expense (2)									1,061,964,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	976,856,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	848,446,000us-gaap_SellingGeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Depreciation and amortization expense									42,344,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	35,826,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	31,534,000us-gaap_DepreciationDepletionAndAmortization / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Asset Impairment Charge									41,520,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	6,542,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	7,276,000us-gaap_AssetImpairmentCharges / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Floorplan interest expense									(41,614,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	(41,667,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	(31,796,000)gpi_FloorPlanInterestExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Other interest expense, net									(49,693,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	(38,971,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	(37,465,000)us-gaap_InterestExpenseOther / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Other Expenses										(789,000)us-gaap_OtherExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Gains (Losses) on Extinguishment of Debt									(46,403,000)us-gaap_GainsLossesOnExtinguishmentOfDebt / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Income before income taxes									164,400,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	191,895,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	160,735,000us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Provision for income taxes									(71,396,000)us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	77,903,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	60,526,000us-gaap_IncomeTaxExpenseBenefit / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Net income									93,004,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	113,992,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	100,209,000us-gaap_NetIncomeLoss / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Capital expenditures									97,709,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	69,216,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	61,961,000gpi_Capitalexpenditures / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember
Total assets	$ 4,141,492,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember				$ 3,819,478,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember				$ 4,141,492,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember	$ 3,819,478,000us-gaap_Assets / us-gaap_StatementBusinessSegmentsAxis = us-gaap_ConsolidatedEntitiesMember

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Capital expenditures

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Interest expense incurred on borrowings under the floorplan line of the credit facility and arrangements with vehicle manufacturer affiliates for the financing of specific new, used and rental vehicle inventory. Interest expense also includes the net impact of interest rate swap settlements during the period, which are designed to hedge exposure to variable interest rates.

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Aggregate revenue recognized during the period derived from new vehicles sold to retail customers. Revenues from new vehicle retail sales are recognized upon completion of the sale and delivery to the customer. Conditions to completing a sale include having an agreement with the customer, including pricing, and the sales price must be reasonably expected to be collected.

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Aggregate revenue recognized during the period derived from parts sold to retail and wholesale customers, as well as performance of vehicle services and repairs. Revenues from new vehicle retail sales are recognized upon completion of the sale and delivery to the customer. Conditions to completing a sale include having an agreement with the customer, including pricing, and the sales price must be reasonably expected to be collected.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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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.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Interest expense on all other items not previously classified. For example, includes dividends associated with redeemable preferred stock of a subsidiary that is treated as a liability in the parent's consolidated balance sheet.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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