Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 11,303.4	$ 10,780.0
Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	11,160.1	10,649.9
Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	108.8	90.8
At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	34.5	39.3
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,728.5	2,342.3
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,453.4	1,464.6
Dealer | Performing | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	2,723.8	2,329.5
Dealer | Performing | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,450.9	1,462.1
Dealer | Watch | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4.7	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	2.5	2.5
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6,022.5	5,857.5
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,099.0	1,115.6
Customer Retail | Performing | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5,902.9	5,759.0
Customer Retail | Performing | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,082.5	1,099.3
Customer Retail | Watch | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	94.6	70.0
Customer Retail | Watch | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	9.5	8.2
Customer Retail | At-risk | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	25.0	28.5
Customer Retail | At-risk | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 7.0	$ 8.1