Pre-Tax Effects of (Loss) Gain on Cash Flow Hedges Recognized in OCI (Detail) - Derivative Contracts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest-Rate Contracts
Derivative [Line Items]
(Loss) gain recognized in OCI	$ (110.5)	$ 19.1	$ 83.2
Foreign-exchange contracts
Derivative [Line Items]
(Loss) gain recognized in OCI	(63.9)	15.7	(20.4)
Truck, Parts and Other | Foreign-exchange contracts
Derivative [Line Items]
(Loss) gain recognized in OCI	(65.7)	41.2	(18.5)
Financial Services | Interest-Rate Contracts
Derivative [Line Items]
(Loss) gain recognized in OCI	(110.5)	19.1	83.2
Financial Services | Foreign-exchange contracts
Derivative [Line Items]
(Loss) gain recognized in OCI	$ 1.8	$ (25.5)	$ (1.9)