Acquisitions (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Jul. 31, 2013 Three Franchises (Three Dealership Locations) [Member] Franchises DealershipLocations	Dec. 31, 2013 Three Franchises (Three Dealership Locations) [Member]	Dec. 31, 2012 Three Franchises (Three Dealership Locations) [Member]	Dec. 31, 2012 2012 Acquisitions [Member] Franchises DealershipLocations	Dec. 31, 2012 Jaguar [Member] Franchises
Business Acquisition [Line Items]
Number of franchises acquired (in franchises)	3			2
Number of dealership locations acquired (in dealership locations)	3			2
Aggregate purchase price	$ 61.8			$ 34.7
Cash paid for acquisition	50.5			26.9
Floor plan borrowings for puchase of related inventory	11.3			7.8
Goodwill and manufacturer franchise rights		$ 29.6	$ 11.6
Goodwill and manufacturer franchise rights, period for federal and state tax deductions		15 years
Number of franchises awarded (in franchises)					1