(Income) Expense Recognized in Earnings Related to Economic Hedges (Detail) - Foreign-exchange contracts - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative [Line Items]
(Income) Expense recognized in earnings	$ 1.2	$ (14.3)
Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	1.0	(1.7)
Truck, Parts and Other | Interest and other expenses, net
Derivative [Line Items]
(Income) Expense recognized in earnings	(0.1)	2.1
Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	2.4	(14.5)
Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	$ (2.1)	$ (0.2)