Summary of Amortized Cost Basis of Financing Receivables by Aging Category (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 6,904.0	$ 6,742.7
Current and up to 30 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	6,901.3	6,740.4
31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2.3	2.1
Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	0.4	0.2
Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2,308.8	2,200.3
Dealer | Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	762.1	737.6
Dealer | Wholesale | Current and up to 30 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	762.1	737.6
Dealer | Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,546.7	1,462.7
Dealer | Retail | Current and up to 30 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	1,546.7	1,462.7
Customer Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	4,595.2	4,542.4
Customer Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	3,919.7	3,855.2
Customer Retail | Fleet | Current and up to 30 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	3,917.6	3,853.5
Customer Retail | Fleet | 31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	2.0	1.7
Customer Retail | Fleet | Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	0.1
Customer Retail | Owner Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	675.5	687.2
Customer Retail | Owner Operator | Current and up to 30 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	674.9	686.6
Customer Retail | Owner Operator | 31 - 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	0.3	0.4
Customer Retail | Owner Operator | Greater than 60 days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, current and up to 30 days past due	$ 0.3	$ 0.2