Expense (Income) Recognized in Earnings Related to Foreign-Exchange Contracts (Detail) - Foreign-exchange contracts - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
(Income) Expense recognized in earnings	$ 70.1	$ 1.2
Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	3.3	1.0
Truck, Parts and Other | Interest and other (income) expense, net
Derivative [Line Items]
(Income) Expense recognized in earnings	31.5	(0.1)
Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	39.2	2.4
Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	$ (3.9)	$ (2.1)