XML 70 R51.htm IDEA: XBRL DOCUMENT v2.4.1.9
Detail of Certain Balance Sheet Accounts (Inventories) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Summary of inventories    
Lower of cost or market reserves $ 5,955us-gaap_InventoryValuationReserves $ 6,362us-gaap_InventoryValuationReserves
Inventories, net 1,547,436us-gaap_InventoryNet 1,556,705us-gaap_InventoryNet
Inventory, Gross 1,553,391us-gaap_InventoryGross 1,563,067us-gaap_InventoryGross
New vehicles [Member]    
Summary of inventories    
Inventory, Gross 1,086,597us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_NewVehiclesMember		 1,137,478us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_NewVehiclesMember
Used vehicles [Member]    
Summary of inventories    
Inventory, Gross 287,979us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_UsedVehiclesMember		 254,939us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_UsedVehiclesMember
Rental vehicles [Member]    
Summary of inventories    
Inventory, Gross 110,878us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_RentalVehiclesMember		 103,184us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_RentalVehiclesMember
Parts, accessories and other [Member]    
Summary of inventories    
Inventory, Gross $ 67,937us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_PartsAccessoriesAndOtherMember		 $ 67,466us-gaap_InventoryGross
/ gpi_InventoriesAxis
= gpi_PartsAccessoriesAndOtherMember