Acquisitions and Dispositions (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) franchise dealership	Jun. 30, 2017 franchise dealerships dealership
Acquisitions and Dispositions (Textual) [Abstract]
Aggregate consideration paid | $	$ 80.0
Cash received in acquisition | $	$ 5.1
United Kingdom
Acquisitions and Dispositions (Textual) [Abstract]
Number of dealerships acquired | dealership	5
Number of franchises acquired	8
Number of dealerships opened | dealership		1
Number of franchises awarded	1	1
Number of franchises disposed	1
United States
Acquisitions and Dispositions (Textual) [Abstract]
Number of dealerships acquired | dealership	2
Number of franchises acquired	2
Number of dealerships disposed | dealership	1
Number of franchises disposed	2
Brazil
Acquisitions and Dispositions (Textual) [Abstract]
Number of dealerships acquired | dealership	1
Number of franchises acquired	1
Number of dealerships disposed | dealerships		2
Number of franchises disposed		2