Revenues - Retail Commercial Truck Dealership (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenues
Total revenues	$ 7,769.2	$ 8,053.0	$ 8,032.5	$ 7,953.8	$ 8,077.6	$ 7,929.5	$ 8,065.0	$ 7,792.7	$ 31,808.5	$ 31,864.8	$ 30,916.5
Retail commercial truck dealership
Revenues
Total revenues									3,411.3	3,521.1	3,684.3
New vehicle | Retail commercial truck dealership
Revenues
Total revenues									2,252.5	2,359.5	2,480.2
Used vehicle | Retail commercial truck dealership
Revenues
Total revenues									228.7	227.0	229.9
Finance and insurance, net | Retail commercial truck dealership
Revenues
Total revenues									15.1	18.8	21.9
Service and parts | Retail commercial truck dealership
Revenues
Total revenues									892.4	886.3	907.3
Other | Retail commercial truck dealership
Revenues
Total revenues									$ 22.6	$ 29.5	$ 45.0