Schedule of Revenues by Major Sources (Detail) - Truck, Parts and Other - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	$ 6,913.7	$ 8,235.0
Trucks
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	5,225.8	6,541.0
Trucks | Truck Sales
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	4,971.7	6,304.7
Trucks | Revenues from extended warranties, operating leases and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	254.1	236.3
Parts Subsegment
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	1,689.9	1,675.9
Parts Subsegment | Parts
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	1,637.6	1,625.6
Parts Subsegment | Revenues from dealer services and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	52.3	50.3
Intersegment Eliminations and Other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	$ (2.0)	$ 18.1