Finance Receivables Evaluated and the Associated Allowances Determined Individually and Collectively (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	$ 14.0	$ 15.4
Allowance for impaired finance receivables determined individually	1.6	2.1
Recorded investment for finance receivables evaluated collectively	6,247.6	6,017.4
Allowance for finance receivables determined collectively	59.7	57.1
Dealer \| Wholesale
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually
Allowance for impaired finance receivables determined individually
Recorded investment for finance receivables evaluated collectively	1,336.4	1,179.0
Allowance for finance receivables determined collectively	3.2	3.1
Dealer \| Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually
Allowance for impaired finance receivables determined individually
Recorded investment for finance receivables evaluated collectively	1,245.2	1,256.1
Allowance for finance receivables determined collectively	8.3	8.4
Customer Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	14.0	15.4
Allowance for impaired finance receivables determined individually	1.6	2.1
Recorded investment for finance receivables evaluated collectively	3,666.0	3,582.3
Allowance for finance receivables determined collectively	$ 48.2	$ 45.6

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

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- Definition

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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