Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 12,055.8	$ 10,780.0
Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	11,929.6	10,649.9
Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	76.3	90.8
At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	49.9	39.3
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,907.4	2,342.3
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,645.6	1,464.6
Dealer | Performing | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,897.3	2,329.5
Dealer | Performing | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,643.3	1,462.1
Dealer | Watch | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	10.1	12.6
Dealer | At-risk | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables		0.2
Dealer | At-risk | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2.3	2.5
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6,347.7	5,857.5
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,155.1	1,115.6
Customer Retail | Performing | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6,251.0	5,759.0
Customer Retail | Performing | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,138.0	1,099.3
Customer Retail | Watch | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	56.4	70.0
Customer Retail | Watch | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	9.8	8.2
Customer Retail | At-risk | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	40.3	28.5
Customer Retail | At-risk | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 7.3	$ 8.1