Balance Sheet Classification of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (646.8)	$ (688.7)
Truck, Parts and Other | Other current assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net		134.8
Truck, Parts and Other | Other Noncurrent Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	135.7	16.0
Truck, Parts and Other | Accounts payable, accrued expenses and other
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities		(0.9)
Truck, Parts and Other | Other liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(25.0)	(87.2)
Financial Services | Other Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	44.9	75.0
Financial Services | Deferred Taxes And Other Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (802.4)	$ (826.4)