Balance Sheet Classifications, Fair Value, Gross and Pro-Forma Net Amounts of Derivative Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
ASSETS
Derivative assets	$ 31.0	$ 48.0
Pro-forma net amount	20.2	31.7
LIABILITIES
Derivative liabilities	66.6	68.6
Pro-forma net amount	55.8	52.3
Interest Rate Contract \| Financial Services
ASSETS
Less amounts not offset in financial instruments	(10.6)	(16.1)
LIABILITIES
Less amounts not offset in financial instruments	(10.6)	(16.1)
Foreign-exchange contracts \| Truck, Parts and Other
ASSETS
Less amounts not offset in financial instruments	(0.2)	(0.2)
LIABILITIES
Less amounts not offset in financial instruments	(0.2)	(0.2)
Designated as Hedging Instrument
ASSETS
Derivative assets	30.6	46.3
LIABILITIES
Derivative liabilities	63.6	68.3
Designated as Hedging Instrument \| Interest Rate Contract \| Financial Services \| Other Assets
ASSETS
Derivative assets	30.5	46.3
Designated as Hedging Instrument \| Interest Rate Contract \| Financial Services \| Deferred Taxes And Other Liabilities
LIABILITIES
Derivative liabilities	62.0	67.7
Designated as Hedging Instrument \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets	0.1
Designated as Hedging Instrument \| Foreign-exchange contracts \| Truck, Parts and Other \| Accounts Payable Accrued Expenses And Other Current Liabilities
LIABILITIES
Derivative liabilities	1.6	0.6
Not Designated as Hedging Instrument
ASSETS
Derivative assets	0.4	1.7
LIABILITIES
Derivative liabilities	3.0	0.3
Not Designated as Hedging Instrument \| Interest Rate Contract \| Financial Services \| Deferred Taxes And Other Liabilities
LIABILITIES
Derivative liabilities	0.5
Not Designated as Hedging Instrument \| Foreign-exchange contracts \| Financial Services \| Other Assets
ASSETS
Derivative assets	0.1	1.1
Not Designated as Hedging Instrument \| Foreign-exchange contracts \| Financial Services \| Deferred Taxes And Other Liabilities
LIABILITIES
Derivative liabilities	1.9	0.1
Not Designated as Hedging Instrument \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets	0.3	0.6
Not Designated as Hedging Instrument \| Foreign-exchange contracts \| Truck, Parts and Other \| Accounts Payable Accrued Expenses And Other Current Liabilities
LIABILITIES
Derivative liabilities	$ 0.6	$ 0.2

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after offset of derivative liability, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, before offset against an obligation to return collateral under a master netting arrangement. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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- Definition

Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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