Balance Sheet Classifications of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Assets Net	$ 1,023.7	$ 963.9
Deferred Tax Liabilities	(76.3)	(31.8)
Truck, Parts and Other | Other Noncurrent Assets
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Assets Net	485.2	502.6
Truck, Parts and Other | Other liabilities
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Liabilities	(102.7)	(78.8)
Financial Services | Other Assets
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Assets Net	60.1	88.3
Financial Services | Deferred Taxes and Other Liabilities
Schedule Of Deferred Income Tax Assets And Liabilities [Line Items]
Deferred Tax Liabilities	$ (518.9)	$ (543.9)