Acquisitions and Dispositions Acquisitions and Dispositions (Details textuals)	9 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Acquisitions and Dispositions (Textual) [Abstract]
Business Combination, Consideration Transferred		$ 336,600,000
Gain (Loss) on Disposition of Business	$ 700,000.0
U.S. [Member]
Acquisitions and Dispositions (Textual) [Abstract]
Number of Franchises Disposed	1
Number Of Dealerships Acquired	3	7
Number of Franchises Awarded		2
Business Acquisition Purchase Price Allocation Goodwill	$ 103,800,000
Number of Dealerships Disposed	1
U.K. [Member]
Acquisitions and Dispositions (Textual) [Abstract]
Number Of Dealerships Acquired		3
Business Acquisition Purchase Price Allocation Goodwill	$ 18,500,000
Brazil [Member]
Acquisitions and Dispositions (Textual) [Abstract]
Number of Franchises Disposed	2
Number Of Dealerships Acquired		1
Number of Franchises Awarded		1
Business Acquisition Purchase Price Allocation Goodwill	$ 0