Balance Sheet Classifications, Fair Value, Gross and Pro Forma Net Amounts of Derivative Financial Instruments (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
ASSETS
Derivative assets	$ 19.7	$ 20.5
Pro forma net amount	8.4	6.4
LIABILITIES
Derivative liabilities	115.9	159.9
Pro forma net amount	104.6	145.8
Interest-Rate Contracts \| Financial Services
ASSETS
Less amounts not offset in financial instruments	(6.9)	(12.0)
LIABILITIES
Less amounts not offset in financial instruments	(6.9)	(12.0)
Foreign-exchange contracts \| Truck, Parts and Other
ASSETS
Less amounts not offset in financial instruments	(4.4)	(2.1)
LIABILITIES
Less amounts not offset in financial instruments	(4.4)	(2.1)
Designated under hedge accounting
ASSETS
Derivative assets	19.6	19.1
LIABILITIES
Derivative liabilities	113.9	153.2
Designated under hedge accounting \| Interest-Rate Contracts \| Financial Services \| Other Assets
ASSETS
Derivative assets	10.4	16.4
Designated under hedge accounting \| Interest-Rate Contracts \| Financial Services \| Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities	88.8	116.1
Designated under hedge accounting \| Foreign-exchange contracts \| Financial Services \| Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities		1.2
Designated under hedge accounting \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets	9.2	2.7
Designated under hedge accounting \| Foreign-exchange contracts \| Truck, Parts and Other \| Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	25.1	35.9
Not designated as hedging instruments
ASSETS
Derivative assets	0.1	1.4
LIABILITIES
Derivative liabilities	2.0	6.7
Not designated as hedging instruments \| Foreign-exchange contracts \| Financial Services \| Other Assets
ASSETS
Derivative assets	0.1	0.3
Not designated as hedging instruments \| Foreign-exchange contracts \| Financial Services \| Deferred Taxes and Other Liabilities
LIABILITIES
Derivative liabilities		3.4
Not designated as hedging instruments \| Foreign-exchange contracts \| Truck, Parts and Other \| Other current assets
ASSETS
Derivative assets		1.1
Not designated as hedging instruments \| Foreign-exchange contracts \| Truck, Parts and Other \| Accounts payable, accrued expenses and other
LIABILITIES
Derivative liabilities	$ 2.0	$ 3.3

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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