Goodwill and Intangible Assets (Goodwill) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Goodwill [Line Items]
Goodwill impairment	$ 0		$ 0		$ 0
Goodwill [Roll Forward]
Goodwill, beginning balance	1,172.2	[1]	1,142.4	[1]
Acquisitions and other adjustments	65.2		29.8
Goodwill, ending balance	1,237.4	[1]	1,172.2	[1]	1,142.4	[1]
Accumulated impairment losses	1,470.0		1,470.0		1,470.0
Accumulated impairment losses, after-tax	1,250.0		1,250.0		1,250.0
Goodwill	1,237.4	[1]	1,172.2	[1]	1,142.4	[1]
Franchise rights impairment	4.2		0		0
Goodwill [Member]
Goodwill [Line Items]
Date of Annual Goodwill and Indefinite Lived Intangible Assets Impairment Test	April 30		April 30		April 30
Reporting Unit, Domestic [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	156.4	[1]	156.4	[1]
Acquisitions and other adjustments	8.8		0
Goodwill, ending balance	165.2	[1]	156.4	[1]
Accumulated impairment losses	140.0		140.0		140.0
Accumulated impairment losses, after-tax	119.0		119.0		119.0
Goodwill	165.2	[1]	156.4	[1]
Reporting Unit, Import [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	518.4	[1]	503.5	[1]
Acquisitions and other adjustments	15.8		14.9
Goodwill, ending balance	534.2	[1]	518.4	[1]
Goodwill	534.2	[1]	518.4	[1]
Reporting Unit, Premium Luxury [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	497.4	[1],[2]	482.5	[1],[2]
Acquisitions and other adjustments	40.6		14.9
Goodwill, ending balance	538.0	[1]	497.4	[1],[2]
Goodwill	538.0	[1]	497.4	[1],[2]
Reporting Unit, Audi [Member]
Goodwill [Roll Forward]
Goodwill, ending balance					13.2
Goodwill					13.2
Goodwill Corporate and Other [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	0	[1]	0	[1]
Acquisitions and other adjustments	0		0
Goodwill, ending balance	0	[1]	0	[1]
Goodwill	$ 0	[1]	$ 0	[1]

[1] Net of accumulated impairment losses of $1.47 billion ($1.25 billion after-tax) associated with our single reporting unit (prior to September 30, 2008, our reporting unit structure was comprised of a single reporting unit) and $140.0 million ($119.0 million after-tax) associated with our Domestic reporting unit, both of which were recorded during the year ended December 31, 2008.

[2] Amounts include the reclassification of $13.2 million from the Import segment to the Premium Luxury segment in connection with the change in segment presentation for our Audi franchises.