Amortized Cost Basis of Financing Receivables by Aging Category (Detail) - Financial Services - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 11,666.8	$ 11,748.5
Finance Receivables, Total	11,704.8	11,796.2
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	12.5	18.8
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	25.5	28.9
Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	3,594.1	3,715.5
Dealer | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,939.7	2,012.4
Finance Receivables, Total	1,939.8	2,012.4
Dealer | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,654.3	1,703.1
Finance Receivables, Total	1,654.3	1,703.1
Dealer | 31 - 60 days past due | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	0.1
Customer Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Finance Receivables, Total	8,110.7	8,080.7
Customer Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	6,727.5	6,718.3
Finance Receivables, Total	6,754.1	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	1,345.3	1,314.7
Finance Receivables, Total	1,356.6	1,327.1
Customer Retail | 31 - 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	7.4	12.3
Customer Retail | 31 - 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	5.0	6.5
Customer Retail | Greater than 60 days past due | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	19.2	23.0
Customer Retail | Greater than 60 days past due | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, past due	$ 6.3	$ 5.9