Segment Information (Details) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) item	Mar. 31, 2015 USD ($)
Segment Reporting Information
Number of reportable Segments \| item	3
Number of geographic operating segments \| item	4
Revenues and segment income by reportable segment
Revenues	$ 4,824.6	$ 4,482.9
Segment income	119.6	115.6
Intersegment Elimination
Revenues and segment income by reportable segment
Revenues	(1.0)	(0.3)
Retail Automotive
Revenues and segment income by reportable segment
Revenues	4,512.9	4,186.8
Segment income	110.4	102.8
Retail Commercial Truck Dealership
Revenues and segment income by reportable segment
Revenues	206.7	192.7
Segment income	5.8	7.4
Other
Revenues and segment income by reportable segment
Revenues	106.0	103.7
Segment income	$ 3.4	$ 5.4

Number of geographic operating segments.

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- Definition

This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=51673353&loc=d3e41242-110953

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 10
-Article 5

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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