Pre-Tax Effects of Derivative Instruments Recognized in OCI (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Interest Rate Contract
Derivative [Line Items]
Loss (gain) recognized in OCI	$ (54.7)	$ 18.2	$ (74.4)	$ 23.7
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	(46.3)	13.3	(61.9)	16.1
Interest Rate Contract | Financial Services
Derivative [Line Items]
Loss (gain) recognized in OCI	(54.7)	18.2	(74.4)	23.7
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	(46.3)	13.3	(61.9)	16.1
Foreign-exchange contracts
Derivative [Line Items]
Loss (gain) recognized in OCI	(1.3)	(0.3)	(2.9)	0.9
Expense (income) reclassified out of accumulated other comprehensive (loss) income into income	0.5	(0.3)	(2.0)	2.7
Foreign-exchange contracts | Truck, Parts and Other
Derivative [Line Items]
Loss (gain) recognized in OCI	(1.3)	(0.3)	(2.9)	0.9
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		0.1	(2.3)	2.7
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)	$ 0.3