(Income) Expense Recognized in Earnings Related to Economic Hedges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest-Rate Contracts
Derivative [Line Items]
(Income) Expense recognized in earnings			$ (1.5)
Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings			(1.5)
Foreign-exchange contracts
Derivative [Line Items]
(Income) Expense recognized in earnings	$ (7.6)	$ 7.9	(10.6)
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	(0.7)	(5.3)	(1.3)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other expenses, net
Derivative [Line Items]
(Income) Expense recognized in earnings	3.0	3.8	0.3
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	(7.6)	4.2	$ (9.6)
Foreign-exchange contracts | Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	$ (2.3)	$ 5.2