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Acquisitions and Dispositions Acquisitions and Dispositions (Details textuals) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Acquisitions and Dispositions (Textual) [Abstract]
Business Combination, Consideration Transferred	$ 120.2	$ 61.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 11.2	$ 3.9
UNITED STATES
Acquisitions and Dispositions (Textual) [Abstract]
Number Of Dealerships Acquired	3
Number of Franchises Acquired	4
Number Of Dealerships Opened	1
Number of Dealerships Disposed		4
Gain (Loss) on Disposition of Business		$ 1.8
UNITED KINGDOM
Acquisitions and Dispositions (Textual) [Abstract]
Number Of Dealerships Acquired	12	12
Number of Franchises Acquired	14	15
Number Of Dealerships Opened	1
Number Of Franchises Awarded	1
BRAZIL
Acquisitions and Dispositions (Textual) [Abstract]
Number Of Dealerships Acquired		1
Number of Franchises Acquired		1
Number Of Dealerships Opened		2
Number Of Franchises Awarded		1
Number of Dealerships Disposed		4
Gain (Loss) on Disposition of Business		$ 0.8
Number of Franchises Disposed	2

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Number of dealerships acquired.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

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Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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