Amount of (Gain) Loss from Derivative Financial Instruments Recorded in Consolidated Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Interest-Rate Contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	$ (140.2)	$ 86.3	$ 7.1
Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(140.2)	86.3	7.1
Foreign-exchange contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(65.4)	45.4	(4.9)
Foreign-exchange contracts | Truck, Parts and Other
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(70.1)	41.9	(4.1)
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues | Not designated as hedging instruments
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss		(5.1)	(1.7)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income) expenses, net | Not designated as hedging instruments
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(10.2)	8.8	0.8
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	4.7	3.5	(0.8)
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses | Not designated as hedging instruments
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	9.7	1.7	(8.1)
Cash Flow Hedging | Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(149.5)	76.5	6.1
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Net sales and revenues
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(12.1)	31.9	19.3
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(28.8)	2.2	(15.3)
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income) expenses, net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(9.2)	12.8	(1.4)
Cash Flow Hedging | Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(5.0)	1.8	7.3
Net Investment Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income) expenses, net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(9.8)	(8.7)	(5.8)
Fair Value Hedging | Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	$ 9.3	$ 9.8	$ 1.0