Revenues - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Revenues
Total revenues	$ 7,662.3	$ 7,696.7	$ 15,266.8	$ 15,144.5
Unearned revenue recognized as revenue			$ 161.1
Commercial vehicle distribution and other
Revenues
Payment period			45 days
Total revenues	201.2	189.0	$ 412.7	367.0
Vehicle Sales | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period			30 days
Service and parts | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period			30 days
Service and parts | Commercial vehicle distribution and other
Revenues
Total revenues	68.2	$ 70.9	$ 131.1	$ 137.9
Finance and insurance, net | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period			30 days
Aggregate reserves relating to chargeback activity	$ 50.8		$ 50.8		$ 48.2