Pre-Tax Effects of Derivative Instruments Recognized in OCI (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest Rate Contract
Derivative [Line Items]
Gain (loss) recognized in OCI	$ (38.7)	$ 54.7	$ (30.3)	$ 74.4
Expense (income) reclassified out of AOCI into income	38.5	(46.3)	31.6	(61.9)
Interest Rate Contract | Financial Services
Derivative [Line Items]
Gain (loss) recognized in OCI	(38.7)	54.7	(30.3)	74.4
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	38.5	(46.3)	31.6	(61.9)
Foreign-exchange contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	(3.0)	1.3	(2.8)	2.9
Expense (income) reclassified out of AOCI into income	1.9	0.5	1.9	(2.0)
Foreign-exchange contracts | Truck, Parts and Other
Derivative [Line Items]
Gain (loss) recognized in OCI	(3.0)	1.3	(2.8)	2.9
Foreign-exchange contracts | Truck, Parts and Other | Cost of sales and revenues
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	1.7		1.8	(2.3)
Foreign-exchange contracts | Truck, Parts and Other | Interest and other (income) expense, net
Derivative [Line Items]
Expense (income) reclassified out of AOCI into income	$ 0.2	$ 0.5	$ 0.1	$ 0.3