Inventory And Vehicle Floorplan Payable (Components Of Vehicle Floorplan Payable) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Floorplan Payable [Line Items]
Vehicle floorplan payable	$ 2,869.1	$ 3,029.0
Trade [Member]
Floorplan Payable [Line Items]
Vehicle floorplan payable	1,977.7	2,130.1
Non-Trade [Member]
Floorplan Payable [Line Items]
Vehicle floorplan payable	$ 891.4	$ 898.9

Amounts borrowed to finance the purchase of specific new vehicle inventories with the corresponding manufacturers' captive finance subsidiaries ("trade lenders") and specific new and, to a lesser extent, used vehicle inventories with non-trade lenders (lenders that are not captive finance subsidiaries of the manufacturer).

No definition available.

Name:	an_VehicleFloorplanPayable
Namespace Prefix:	an_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant