Balance Sheet Classifications of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Liabilities	$ (31.8)	$ (349.4)
Truck, Parts and Other | Other Noncurrent Assets
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Assets Net	502.6	199.0
Truck, Parts and Other | Other liabilities
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Liabilities	(78.8)	(75.5)
Financial Services | Other Assets
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Assets Net	88.3	51.0
Financial Services | Deferred Taxes and Other Liabilities
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Liabilities	$ (543.9)	$ (523.9)