Expense (Income) Recognized in Earnings Related to Foreign-Exchange Contracts (Detail) - Foreign-exchange contracts - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Expense (Income) recognized in earnings	$ (4.5)	$ 6.3
Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
Expense (Income) recognized in earnings	0.2	1.2
Truck, Parts and Other | Interest and other (income), net
Derivative [Line Items]
Expense (Income) recognized in earnings	1.5	3.4
Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
Expense (Income) recognized in earnings	$ (6.2)	0.5
Financial Services | Selling, general and administrative
Derivative [Line Items]
Expense (Income) recognized in earnings		$ 1.2