Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Intangible Assets - Information by Segment (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Summary of the changes in the carrying amount of goodwill by reportable segment
Goodwill	$ 1,325.6	$ 1,322.8
Retail Automotive
Summary of the changes in the carrying amount of goodwill by reportable segment
Goodwill	1,094.2
Retail Commercial Truck Dealership
Summary of the changes in the carrying amount of goodwill by reportable segment
Goodwill	147.5
Other
Summary of the changes in the carrying amount of goodwill by reportable segment
Goodwill	$ 83.9