Finance Receivable Evaluated and Determined Individually and Collectively (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis for impaired finance receivables evaluated individually	$ 67.9	$ 87.9
Allowance for impaired finance receivables determined individually	4.5	5.6
Amortized cost basis for finance receivables evaluated collectively	11,308.7	11,708.3
Allowance for finance receivables determined collectively	113.8	118.2
Dealer \| Wholesale
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis for finance receivables evaluated collectively	1,377.1	2,012.4
Allowance for finance receivables determined collectively	2.4	3.4
Dealer \| Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis for impaired finance receivables evaluated individually	1.2	1.2
Amortized cost basis for finance receivables evaluated collectively	1,676.7	1,701.9
Allowance for finance receivables determined collectively	7.7	8.4
Customer Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost basis for impaired finance receivables evaluated individually	66.7	86.7
Allowance for impaired finance receivables determined individually	4.5	5.6
Amortized cost basis for finance receivables evaluated collectively	8,254.9	7,994.0
Allowance for finance receivables determined collectively	$ 103.7	$ 106.4

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=123577603&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.

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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=123577603&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=123577603&loc=SL6953423-111524

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