(Income) Expense Recognized in Earnings Related to Economic Hedges (Detail) - Foreign-exchange contracts - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative [Line Items]
(Income) Expense recognized in earnings	$ (9.1)	$ (4.5)	$ (7.9)	$ (18.8)
Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	0.1	(0.3)	1.1	(2.0)
Truck, Parts and Other | Interest and other expense, net
Derivative [Line Items]
(Income) Expense recognized in earnings	0.9	(0.5)	0.8	1.6
Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	(10.6)	(3.3)	(8.2)	(17.8)
Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	$ 0.5	$ (0.4)	$ (1.6)	$ (0.6)