Revenues - Retail Commercial Truck Dealership (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues
Total revenues	$ 5,971.6	$ 5,967.6	$ 14,631.8	$ 17,287.8
Retail Commercial Truck Dealership
Revenues
Total revenues	590.9	692.3	1,481.5	1,451.4
New vehicle | Retail Commercial Truck Dealership
Revenues
Total revenues	376.6	476.2	930.4	979.6
Used vehicle | Retail Commercial Truck Dealership
Revenues
Total revenues	63.9	36.1	135.4	87.8
Finance and insurance, net | Retail Commercial Truck Dealership
Revenues
Total revenues	4.1	3.1	10.5	9.0
Service and parts | Retail Commercial Truck Dealership
Revenues
Total revenues	122.1	154.6	358.1	340.7
Other | Retail Commercial Truck Dealership
Revenues
Total revenues	$ 24.2	$ 22.3	$ 47.1	$ 34.3