Cumulative Effect of Change in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings	$ 17,751.0	$ 15,780.3
Truck, Parts and Other
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Inventories, net	2,367.1	2,576.7
Other liabilities	$ 1,874.0	$ 2,121.9