Amount of Loss (Gain) from Derivative Financial Instruments Recorded in Consolidated Statements of Comprehensive Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Interest-Rate Contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	$ (56.4)	$ (35.4)	$ (99.4)	$ (45.8)
Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(56.4)	(35.4)	(99.4)	(45.8)
Foreign-exchange contracts
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(7.2)	13.5	9.5	23.9
Foreign-exchange contracts | Truck, Parts and Other
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(7.1)	13.8	14.0	24.6
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	0.4	17.8	0.3	8.8
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income), net | Not designated as hedging instruments
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(5.8)	(0.6)	(4.5)	1.0
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(0.1)	(0.3)	(4.5)	(0.7)
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	2.9	(0.3)	3.1	(0.7)
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	(56.2)	(35.4)	(99.3)	(45.9)
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Sales
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	2.0	1.3	17.1	14.9
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	(6.2)	(3.5)	(3.5)	2.5
Cash Flow Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income), net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	3.9	(0.5)	8.8	(0.2)
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	(3.0)		(7.6)
Net Investment Hedging | Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income), net
Derivative Instruments Gain Loss [Line Items]
Derivatives designated as hedging instruments (gain) loss	(1.4)	$ (0.7)	(4.2)	(2.4)
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	$ (0.2)		$ (0.1)	$ 0.1