Interim Financial Statements (Business and Basis of Presentation) (Details)	9 Months Ended
	Sep. 30, 2019 brand store franchises
Product Information [Line Items]
Owned and operated new vehicle franchises | franchises	319
Number of stores (approximate number for total locations)	325
Number of brands | brand	31
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)	233
Collision Centers [Member]
Product Information [Line Items]
Number of stores (approximate number for total locations)	82