Inventories - Schedule of Inventory (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Inventory [Line Items]
Total inventories	$ 4,814.7	$ 4,710.7
Retail automotive dealership new vehicles
Inventory [Line Items]
Total inventories	2,390.8	2,383.3
Retail automotive dealership used vehicles
Inventory [Line Items]
Total inventories	1,253.5	1,146.7
Retail automotive parts, accessories, and other
Inventory [Line Items]
Total inventories	186.3	173.2
Retail commercial truck dealership vehicles and parts
Inventory [Line Items]
Total inventories	492.8	518.4
Commercial vehicle distribution vehicles, parts, and engines
Inventory [Line Items]
Total inventories	$ 491.3	$ 489.1