Amortized Cost Basis of Financing Receivables by Aging Category (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 11,234.7	$ 11,990.8
Finance Receivables, Total	11,293.3	12,055.8
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	25.5	31.7
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	33.1	33.3
Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	3,729.9
Dealer | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2,079.7	2,907.4
Finance Receivables, Total	2,079.7	2,907.4
Dealer | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,650.2	1,645.6
Finance Receivables, Total	1,650.2	1,645.6
Customer Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	7,563.4
Customer Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	6,277.4	6,297.1
Finance Receivables, Total	6,319.8	6,347.7
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,227.4	1,140.7
Finance Receivables, Total	1,243.6	1,155.1
Customer Retail | 31 - 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	18.1	23.0
Customer Retail | 31 - 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	7.4	8.7
Customer Retail | Greater than 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	24.3	27.6
Customer Retail | Greater than 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	$ 8.8	$ 5.7