Financing Receivables by Aging Category (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 11,529.6	$ 10,745.4
Financing Receivables	11,629.6	10,780.0
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	56.0	18.0
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	44.0	16.6
Dealer | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2,778.7	2,342.1
Financing Receivables	2,813.5	2,342.3
Dealer | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,559.9	1,464.6
Financing Receivables	1,559.9	1,464.6
Dealer | 31 - 60 days past due | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	34.8	0.1
Dealer | Greater than 60 days past due | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due		0.1
Customer Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	6,080.0	5,835.6
Financing Receivables	6,132.5	5,857.5
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,111.0	1,103.1
Financing Receivables	1,123.7	1,115.6
Customer Retail | 31 - 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	14.5	11.2
Customer Retail | 31 - 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	6.7	6.7
Customer Retail | Greater than 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	38.0	10.7
Customer Retail | Greater than 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	$ 6.0	$ 5.8