Schedule of Revenues by Major Sources (Detail) - Truck, Parts and Other - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	$ 4,778.0	$ 6,138.1
Trucks
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	3,757.6	5,107.3
Trucks | Truck Sales
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	3,583.6	4,913.6
Trucks | Revenues from extended warranties, operating leases and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	174.0	193.7
Parts Subsegment
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	998.6	1,004.7
Parts Subsegment | Parts
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	970.0	976.6
Parts Subsegment | Revenues from dealer services and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	28.6	28.1
Winch Sales and Other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	$ 21.8	$ 26.1