Revenues - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Revenues
Total revenues	$ 7,695.3	$ 7,590.8	$ 22,962.1	$ 22,735.3
Unearned revenue recognized as revenue			$ 184.8
Commercial vehicle distribution and other
Revenues
Payment period			45 days
Total revenues	206.6	186.8	$ 619.3	553.8
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	74.0	$ 68.8	$ 205.1	$ 206.7
Finance and insurance, net | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period			30 days
Aggregate reserves relating to chargeback activity	$ 53.6		$ 53.6		$ 48.2