Pre-Tax Effects of Derivative Instruments Recognized in OCI (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest Rate Contract
Derivative [Line Items]
Loss (gain) recognized in OCI	$ 33.1	$ 5.7	$ (41.3)	$ 29.4
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	32.8	1.6	(29.1)	17.7
Interest Rate Contract | Financial Services
Derivative [Line Items]
Loss (gain) recognized in OCI	33.1	5.7	(41.3)	29.4
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	32.8	1.6	(29.1)	17.7
Foreign-exchange contracts
Derivative [Line Items]
Loss (gain) recognized in OCI	4.6	1.3	1.7	2.2
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	1.3	2.0	(0.7)	4.7
Foreign-exchange contracts | Truck, Parts and Other
Derivative [Line Items]
Loss (gain) recognized in OCI	4.6	1.3	1.7	2.2
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	1.8	1.6	(0.5)	4.3
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (expense) income, net
Derivative [Line Items]
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	$ (0.5)	$ 0.4	$ (0.2)	$ 0.4