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	Jun. 30, 2016	Dec. 31, 2015
Intangible assets
Goodwill	$ 1,313.4	$ 1,323.2
Retail Automotive
Intangible assets
Goodwill	1,069.2
Retail Commercial Truck Dealership
Intangible assets
Goodwill	161.2
Other
Intangible assets
Goodwill	$ 83.0