Schedule of Revenues by Major Sources (Detail) - Truck, Parts and Other - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues	$ 5,136.0	$ 4,538.4	$ 2,701.9	$ 4,778.0	$ 5,710.9	$ 6,004.2	$ 6,266.5	$ 6,138.1	$ 17,154.3	$ 24,119.7
Trucks
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									13,164.8	19,989.5
Trucks | Truck Sales
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									12,466.9	19,225.2
Trucks | Revenues from extended warranties, operating leases and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									697.9	764.3
Parts Subsegment
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									3,912.9	4,024.9
Parts Subsegment | Parts
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									3,803.3	3,912.1
Parts Subsegment | Revenues from dealer services and other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									109.6	112.8
Winch Sales and Other
Entity Wide Information Revenue From External Customer [Line Items]
Total sales and revenues									$ 76.6	$ 105.3