Balance Sheet Classifications, Fair Value, Gross and Pro Forma Net Amounts of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
ASSETS
Derivative assets	$ 94.9	$ 207.0
Pro forma net amount	$ 90.0	$ 194.7
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Assets	Assets
LIABILITIES
Derivative liabilities	$ 93.0	$ 46.7
Pro forma net amount	$ 88.1	$ 34.4
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Liabilities	Liabilities
Interest-Rate Contracts | Financial Services
ASSETS
Less amounts not offset in financial instruments	$ (3.3)	$ (11.4)
LIABILITIES
Less amounts not offset in financial instruments	(3.3)	(11.4)
Foreign-exchange contracts | Truck, Parts and Other
ASSETS
Less amounts not offset in financial instruments	(1.4)	(0.9)
LIABILITIES
Less amounts not offset in financial instruments	(1.4)	(0.9)
Commodity contracts | Truck, Parts and Other
ASSETS
Less amounts not offset in financial instruments	(0.2)
LIABILITIES
Less amounts not offset in financial instruments	(0.2)
Designated under hedge accounting
ASSETS
Derivative assets	94.5	205.6
LIABILITIES
Derivative liabilities	92.5	44.1
Designated under hedge accounting | Interest-Rate Contracts | Financial Services | Other Assets
ASSETS
Derivative assets	84.8	132.2
Designated under hedge accounting | Interest-Rate Contracts | Financial Services | Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	52.9	41.1
Designated under hedge accounting | Foreign-exchange contracts | Financial Services | Other Assets
ASSETS
Derivative assets		5.8
Designated under hedge accounting | Foreign-exchange contracts | Financial Services | Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	1.9
Designated under hedge accounting | Foreign-exchange contracts | Truck, Parts and Other | Other current assets
ASSETS
Derivative assets	9.5	67.6
Designated under hedge accounting | Foreign-exchange contracts | Truck, Parts and Other | Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	36.3	3.0
Designated under hedge accounting | Commodity contracts | Truck, Parts and Other | Other current assets
ASSETS
Derivative assets	0.2
Designated under hedge accounting | Commodity contracts | Truck, Parts and Other | Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	1.4
Not designated as hedging instruments
ASSETS
Derivative assets	0.4	1.4
LIABILITIES
Derivative liabilities	0.5	2.6
Not designated as hedging instruments | Foreign-exchange contracts | Financial Services | Other Assets
ASSETS
Derivative assets		0.2
Not designated as hedging instruments | Foreign-exchange contracts | Financial Services | Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	0.2	0.2
Not designated as hedging instruments | Foreign-exchange contracts | Truck, Parts and Other | Other current assets
ASSETS
Derivative assets	0.4	1.2
Not designated as hedging instruments | Foreign-exchange contracts | Truck, Parts and Other | Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	$ 0.3	$ 2.4