Product Support Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Product Liability Contingency [Line Items]
Product Warranty Accrual	$ 772.8	$ 630.5	$ 540.7	$ 448.7
Truck, Parts and Other | Accounts Payable Accrued Expenses and Other
Product Liability Contingency [Line Items]
Product Warranty Accrual	355.3	291.7
Truck, Parts and Other | Other liabilities
Product Liability Contingency [Line Items]
Product Warranty Accrual	406.2	327.5
Financial Services | Deferred Taxes And Other Liabilities
Product Liability Contingency [Line Items]
Product Warranty Accrual	$ 11.3	$ 11.3