Pre-Tax Effects of Derivative Instruments Recognized in Earnings and Other Comprehensive (Loss) Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Interest Rate Contract
Derivative [Line Items]
(Gain)/loss recognized in OCI	$ 5.5	$ (0.6)
(Income)/expense reclassified from Accumulated OCI into income	2.8	13.9
Interest Rate Contract | Financial Services
Derivative [Line Items]
(Gain)/loss recognized in OCI	5.5	(0.6)
Interest Rate Contract | Financial Services | Interest and other borrowing expenses
Derivative [Line Items]
(Income)/expense reclassified from Accumulated OCI into income	2.8	13.9
Foreign Exchange Contract
Derivative [Line Items]
(Gain)/loss recognized in OCI	1.2	(4.6)
(Income)/expense reclassified from Accumulated OCI into income	3.0	0.5
Foreign Exchange Contract | Truck and Other
Derivative [Line Items]
(Gain)/loss recognized in OCI	1.2	(4.6)
Foreign Exchange Contract | Truck and Other | Cost of sales and revenues
Derivative [Line Items]
(Income)/expense reclassified from Accumulated OCI into income	2.6	0.5
Foreign Exchange Contract | Truck and Other | Interest and other (income) expense, net
Derivative [Line Items]
(Income)/expense reclassified from Accumulated OCI into income	$ 0.4