Compare Currently Reported Amounts and Reported Under LIFO in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings	$ 15,780.3	$ 13,402.4
Truck, Parts and Other
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Inventories, net	$ 2,576.7	$ 2,198.8