Amortized Cost Basis of Financing Receivables by Aging Category (Detail) - Financial Services - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 11,840.4	$ 11,748.5
Finance Receivables, Total	11,872.7	11,796.2
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	11.2	18.8
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	21.1	28.9
Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	3,485.1	3,715.5
Dealer | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,818.3	2,012.4
Finance Receivables, Total	1,818.3	2,012.4
Dealer | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,666.8	1,703.1
Finance Receivables, Total	1,666.8	1,703.1
Customer Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	8,387.6	8,080.7
Customer Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	6,934.3	6,718.3
Finance Receivables, Total	6,956.4	6,753.6
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,421.0	1,314.7
Finance Receivables, Total	1,431.2	1,327.1
Customer Retail | 31 - 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	6.8	12.3
Customer Retail | 31 - 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	4.4	6.5
Customer Retail | Greater than 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	15.3	23.0
Customer Retail | Greater than 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	$ 5.8	$ 5.9