Balance Sheet Classification of Deferred Tax Assets And Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	$ 358.1	$ 421.0
Deferred Tax Liabilities	(1,204.6)	(1,031.3)
Net deferred tax liability	(846.5)	(610.3)
Truck, Parts and Other | Other current assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	122.2	151.2
Truck, Parts and Other | Other Noncurrent Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	33.1	40.9
Truck, Parts and Other | Accounts Payable and Accrued Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(0.6)	(1.7)
Truck, Parts and Other | Other Noncurrent Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(218.7)	(90.7)
Financial Services | Other Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	77.2	72.4
Financial Services | Deferred Taxes And Other Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (859.7)	$ (782.4)