Balance Sheet Classifications, Fair Value, Gross and Pro Forma Net Amounts of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
ASSETS
Derivative assets	$ 68.0	$ 94.7
Pro forma net amount	58.6	89.9
LIABILITIES
Derivative liabilities	26.5	24.6
Pro forma net amount	17.1	19.8
Interest-Rate Contracts \| Financial Services
ASSETS
Less amounts not offset in financial instruments	(7.6)	(3.9)
LIABILITIES
Less amounts not offset in financial instruments	(7.6)	(3.9)
Foreign-exchange contracts \| Truck, Parts and Other
ASSETS
Less amounts not offset in financial instruments	(1.8)	(0.9)
LIABILITIES
Less amounts not offset in financial instruments	(1.8)	(0.9)
Foreign-exchange contracts \| Truck, Parts and Other \| Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	1.4	0.9
Designated under hedge accounting
ASSETS
Derivative assets	66.4	93.4
LIABILITIES
Derivative liabilities	24.8	22.7
Designated under hedge accounting \| Interest-Rate Contracts \| Financial Services \| Other Assets
ASSETS
Derivative assets	62.8	84.5
Designated under hedge accounting \| Interest-Rate Contracts \| Financial Services \| Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	17.3	18.5
Designated under hedge accounting \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets	3.6	8.9
Designated under hedge accounting \| Foreign-exchange contracts \| Truck, Parts and Other \| Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	7.5	4.2
Not designated as hedging instruments
ASSETS
Derivative assets	1.6	1.3
LIABILITIES
Derivative liabilities	1.7	1.9
Not designated as hedging instruments \| Foreign-exchange contracts \| Financial Services \| Other Assets
ASSETS
Derivative assets	0.9	0.9
Not designated as hedging instruments \| Foreign-exchange contracts \| Financial Services \| Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	0.3	1.0
Not designated as hedging instruments \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets	$ 0.7	$ 0.4

Fair value of liability associated with 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.

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