Amount of Loss (Gain) from Derivative Financial Instruments Recorded in Consolidated Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Interest-Rate Contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	$ 63.4	$ (21.7)
Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	63.4	(21.7)
Foreign-exchange contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	2.5	(2.3)
Foreign-exchange contracts | Truck, Parts and Other
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	(3.4)	0.1
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 loss (gain)	(0.7)	0.8
Foreign-exchange contracts | Truck, Parts and Other | Interest and other expense (income), net | Not designated as hedging instruments
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	1.3	0.1
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	5.9	(2.4)
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 loss (gain)	0.1	(0.2)
Cash Flow Hedging | Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	62.4	(24.5)
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 loss (gain)	(2.8)	8.8
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 loss (gain)	(9.5)	(7.4)
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other expense (income), net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	12.4	1.3
Cash Flow Hedging | Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	5.8	(2.2)
Net Investment Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other expense (income), net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	(4.1)	(3.5)
Fair Value Hedging | Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments loss (gain)	$ 1.0	$ 2.8