Inventory And Vehicle Floorplan Payable (Components Of Vehicle Floorplan Payable) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Floorplan Payable [Line Items]
Vehicle floorplan payable	$ 2,748.1	$ 2,540.2
Trade [Member]
Floorplan Payable [Line Items]
Vehicle floorplan payable	1,944.0	1,766.3
Non-Trade [Member]
Floorplan Payable [Line Items]
Vehicle floorplan payable	$ 804.1	$ 773.9