Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 11,629.6	$ 10,780.0
Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	11,468.6	10,649.9
Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	83.1	90.8
At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	77.9	39.3
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,813.5	2,342.3
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,559.9	1,464.6
Dealer | Performing | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,768.7	2,329.5
Dealer | Performing | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,557.6	1,462.1
Dealer | Watch | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	20.5	12.6
Dealer | At-risk | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	24.3	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	6,132.5	5,857.5
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,123.7	1,115.6
Customer Retail | Performing | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6,033.9	5,759.0
Customer Retail | Performing | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,108.4	1,099.3
Customer Retail | Watch | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	54.3	70.0
Customer Retail | Watch | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8.3	8.2
Customer Retail | At-risk | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	44.3	28.5
Customer Retail | At-risk | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 7.0	$ 8.1