Expense or (Income) Recognized in Earnings Related to Economic Hedges (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest Rate Contract
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	$ (1.5)	$ 1.0	$ (4.1)
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	(1.5)	1.0	(4.1)
Foreign-exchange contracts
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	(10.6)	(0.2)	(3.8)
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)	(0.3)	0.2
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	0.3	(0.5)	(2.8)
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	$ (9.6)	$ 0.6	$ (1.2)