Pre-Tax Effects of Derivative Instruments Recognized in OCI (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Interest Rate Contract
Derivative [Line Items]
Gain (loss) recognized in OCI	$ 8.4	$ 19.7
Expense (income) reclassified out of AOCI into income	(6.9)	(15.6)
Interest Rate Contract | Financial Services
Derivative [Line Items]
Gain (loss) recognized in OCI	8.4	19.7
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	(6.9)	(15.6)
Foreign-exchange contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	0.2	1.6
Expense (income) reclassified out of AOCI into income		(2.5)
Foreign-exchange contracts | Truck, Parts and Other
Derivative [Line Items]
Gain (loss) recognized in OCI	0.2	1.6
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	0.1	(2.3)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other expense, net
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	$ (0.1)	$ (0.2)