Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Inventory [Line Items]
Total inventories	$ 3,700.2	$ 3,509.1
Retail automotive dealership new vehicles
Inventory [Line Items]
Total inventories	1,566.6	1,326.5
Retail automotive dealership used vehicles
Inventory [Line Items]
Total inventories	1,114.7	1,279.6
Retail automotive parts, accessories, and other
Inventory [Line Items]
Total inventories	153.3	145.6
Retail commercial truck dealership vehicles and parts
Inventory [Line Items]
Total inventories	494.3	506.2
Commercial vehicle distribution vehicles, parts, and engines
Inventory [Line Items]
Total inventories	$ 371.3	$ 251.2