Expense or (Income) Recognized in Earnings Related to Economic Hedges (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest Rate Contract
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	$ (0.1)	$ 1.6	$ (1.5)	$ 1.5
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	(0.1)	1.6	(1.5)	1.5
Foreign-exchange contracts
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	(5.2)	1.5	(9.0)	(0.1)
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	(1.3)		(0.9)	(0.3)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (expense) income, net
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	0.4	2.0	0.8	(0.4)
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	$ (4.3)	$ (0.5)	$ (8.9)	$ 0.6