Inventory And Vehicle Floorplan Payable (Narrative) (Details) (USD $) In Millions, unless otherwise specified			9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Used Vehicle Floorplan Facilities [Member]	Sep. 30, 2013 Used Vehicle Floorplan Facilities [Member]	Sep. 30, 2014 New Vehicle Floorplan Facilities [Member]	Sep. 30, 2013 New Vehicle Floorplan Facilities [Member]
Floorplan Payable [Line Items]
Vehicle floorplan facilities, average LIBOR-based interest rates			1.70%	1.80%	1.80%	2.00%
Vehicle floorplan facilities, maximum borrowing capacity			$ 275.0		$ 3,500.0
Vehicle floorplan facilities, amount outstanding	2,774.7	3,029.0	189.1		2,600.0
Used vehicle floorplan facilities, remaining borrowing capacity	85.9
Used vehicle floorplan facilities, current borrowing capacity	$ 50.2