Description of Business and Summary of Significant Accounting Policies (Organization and Business, Inventory) (Details)	12 Months Ended
	Dec. 31, 2018 brand store franchises
Product Information [Line Items]
Owned and operated new vehicle franchises | franchises	326
Number of stores (approximate number for total locations)	325
Number of brands | brand	33
Percentage of new vehicle sales from core brands (percent)	92.00%
Dealerships [Member]
Product Information [Line Items]
Number of stores (approximate number for total locations)	239
Collision Centers [Member]
Product Information [Line Items]
Number of stores (approximate number for total locations)	85