Balance Sheet Classification of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (671.7)	$ (646.8)
Truck, Parts and Other | Other Noncurrent Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	119.5	135.7
Truck, Parts and Other | Other liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(6.3)	(25.0)
Financial Services | Other Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	74.6	44.9
Financial Services | Deferred Taxes And Other Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (859.5)	$ (802.4)