Expense or (Income) Recognized in Earnings Related to Economic Hedges (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest Rate Contract
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	$ 0.3	$ (0.1)	$ 0.3	$ (1.4)
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	0.3	(0.1)	0.3	(1.4)
Foreign-exchange contracts
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	5.1	(5.7)	4.9	(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	(0.4)	0.5	(0.2)	0.4
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income) expense, net
Derivative [Line Items]
(Income) or expense recognized in earnings related to economic hedges	1.2	(1.3)	0.3	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	$ (4.9)	$ 4.8	$ (4.6)