Financing Receivables by Aging Category (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 10,494.2	$ 9,612.3
Financing Receivables	10,532.4	9,653.2
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	18.0	18.7
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	20.2	22.2
Dealer \| Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2,229.4	1,880.5
Financing Receivables	2,229.6	1,880.6
Dealer \| Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,373.0	1,358.7
Financing Receivables	1,373.0	1,358.7
Dealer \| 31 - 60 days past due \| Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	0.1	0.0
Dealer \| 31 - 60 days past due \| Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	0.0	0.0
Dealer \| Greater than 60 days past due \| Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	0.1	0.1
Dealer \| Greater than 60 days past due \| Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	0.0	0.0
Customer Retail \| Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	5,820.9	5,365.7
Financing Receivables	5,846.5	5,397.9
Customer Retail \| Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,070.9	1,007.4
Financing Receivables	1,083.3	1,016.0
Customer Retail \| 31 - 60 days past due \| Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	12.4	14.7
Customer Retail \| 31 - 60 days past due \| Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	5.5	4.0
Customer Retail \| Greater than 60 days past due \| Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	13.2	17.5
Customer Retail \| Greater than 60 days past due \| Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	$ 6.9	$ 4.6

Financing receivables that are current.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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Recorded Investment in financing receivables that are past due at the balance sheet date.

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No definition available.

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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
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