Revenues - Retail Commercial Truck Dealership (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues
Total revenues	$ 3,651.1	$ 5,755.8	$ 8,660.2	$ 11,320.2
Retail Commercial Truck Dealership
Revenues
Total revenues	399.2	426.8	890.6	759.1
New vehicle | Retail Commercial Truck Dealership
Revenues
Total revenues	235.5	296.0	553.8	503.4
Used vehicle | Retail Commercial Truck Dealership
Revenues
Total revenues	36.9	27.6	71.5	51.7
Finance and insurance, net | Retail Commercial Truck Dealership
Revenues
Total revenues	3.2	2.9	6.4	5.9
Service and parts | Retail Commercial Truck Dealership
Revenues
Total revenues	111.6	94.6	236.0	186.1
Other | Retail Commercial Truck Dealership
Revenues
Total revenues	$ 12.0	$ 5.7	$ 22.9	$ 12.0