(Income) Expense Recognized in Earnings Related to Economic Hedges (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest-Rate Contracts
Derivative [Line Items]
(Income) Expense recognized in earnings	$ 0.1	$ 0.0	$ 0.0
Interest-Rate Contracts | Truck, Parts and Other | Net sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	0.0	0.0	0.0
Interest-Rate Contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	0.0	0.0	0.0
Interest-Rate Contracts | Truck, Parts and Other | Interest and other expense, net
Derivative [Line Items]
(Income) Expense recognized in earnings	0.0	0.0	0.0
Interest-Rate Contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	0.1	0.0	0.0
Interest-Rate Contracts | Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	0.0	0.0	0.0
Foreign-exchange contracts
Derivative [Line Items]
(Income) Expense recognized in earnings	(11.7)	(7.6)	7.9
Foreign-exchange contracts | Truck, Parts and Other | Net sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	(0.4)	0.0	0.0
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
(Income) Expense recognized in earnings	0.4	(0.7)	(5.3)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other expense, net
Derivative [Line Items]
(Income) Expense recognized in earnings	14.9	3.0	3.8
Foreign-exchange contracts | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income) Expense recognized in earnings	(28.4)	(7.6)	4.2
Foreign-exchange contracts | Financial Services | Selling, general and administrative
Derivative [Line Items]
(Income) Expense recognized in earnings	$ 1.8	$ (2.3)	$ 5.2