Reclassifications Out of Accumulated Other Comprehensive Income (Parenthetical) (Detail) (Truck, Parts and Other, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Schedule of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit pension plans, actuarial (loss), pre-tax expense	$ 10.5	[1]
Cost of sales and revenues
Schedule of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit pension plans, actuarial (loss), pre-tax expense	5.7	[1]
SG&A
Schedule of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit pension plans, actuarial (loss), pre-tax expense	$ 4.8	[1]

[1] Amounts in parentheses indicate reductions in expenses in the Consolidated Statements of Comprehensive Income. Amounts without parenthesis indicate expenses in the Consolidated Statements of Comprehensive Income.