Inventories - Schedule of Inventory (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Inventory [Line Items]
Total inventories	$ 4,424.1	$ 4,293.1
Retail automotive dealership new vehicles
Inventory [Line Items]
Total inventories	2,001.4	1,951.3
Retail automotive dealership used vehicles
Inventory [Line Items]
Total inventories	1,161.1	1,186.3
Retail automotive parts, accessories, and other
Inventory [Line Items]
Total inventories	162.7	156.2
Retail commercial truck dealership vehicles and parts
Inventory [Line Items]
Total inventories	645.1	543.7
Commercial vehicle distribution vehicles, parts, and engines
Inventory [Line Items]
Total inventories	$ 453.8	$ 455.6