Amortized Cost Basis of Finance Receivables and Charge-offs by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	$ 5,175.5	$ 4,428.5
Financing Receivable Originated In Current Fiscal Year	4,474.8	5,942.3
Financing Receivable, Originated One Year before Current Fiscal Year	4,735.5	3,587.6
Financing Receivable, Originated Two Years before Current Fiscal Year	2,710.0	1,888.0
Financing Receivable, Originated Three Years before Current Fiscal Year	1,270.6	1,038.2
Financing Receivable, Originated Four Years before Current Fiscal Year	598.8	444.3
Financed Receivables, By Origination Year, Prior	305.8	199.3
Finance Receivables, Total	19,271.0	17,528.2
Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans		0.2
Financing Receivable Originated In Current Fiscal Year	1.1	1.5
Financing Receivable, Originated One Year before Current Fiscal Year	11.9	10.5
Financing Receivable, Originated Two Years before Current Fiscal Year	11.1	6.6
Financing Receivable, Originated Three Years before Current Fiscal Year	6.0	4.7
Financing Receivable, Originated Four Years before Current Fiscal Year	3.1	4.2
Financed Receivables, By Origination Year, Prior	5.7	0.9
Finance Receivables, Total	38.9	28.6
Dealer
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	5,175.5	4,428.5
Financing Receivable Originated In Current Fiscal Year	490.2	789.1
Financing Receivable, Originated One Year before Current Fiscal Year	704.6	520.0
Financing Receivable, Originated Two Years before Current Fiscal Year	441.0	291.2
Financing Receivable, Originated Three Years before Current Fiscal Year	212.3	162.8
Financing Receivable, Originated Four Years before Current Fiscal Year	121.9	161.8
Financed Receivables, By Origination Year, Prior	173.6	125.2
Finance Receivables, Total	7,319.1	6,478.6
Dealer | Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans		0.2
Finance Receivables, Total		0.2
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	4,973.5	4,147.8
Finance Receivables, Total	4,973.5	4,147.8
Dealer | Wholesale | Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans		0.2
Finance Receivables, Total		0.2
Dealer | Wholesale | Performing
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	4,960.7	4,129.8
Finance Receivables, Total	4,960.7	4,129.8
Dealer | Wholesale | Watch
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	12.4	18.0
Finance Receivables, Total	12.4	18.0
Dealer | Wholesale | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	0.4
Finance Receivables, Total	0.4
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	202.0	280.7
Financing Receivable Originated In Current Fiscal Year	490.2	789.1
Financing Receivable, Originated One Year before Current Fiscal Year	704.6	520.0
Financing Receivable, Originated Two Years before Current Fiscal Year	441.0	291.2
Financing Receivable, Originated Three Years before Current Fiscal Year	212.3	162.8
Financing Receivable, Originated Four Years before Current Fiscal Year	121.9	161.8
Financed Receivables, By Origination Year, Prior	173.6	125.2
Finance Receivables, Total	2,345.6	2,330.8
Dealer | Retail | Performing
Financing Receivable, Recorded Investment [Line Items]
Financed Receivables, By Origination Year, Loans	202.0	280.7
Financing Receivable Originated In Current Fiscal Year	489.2	789.1
Financing Receivable, Originated One Year before Current Fiscal Year	679.6	520.0
Financing Receivable, Originated Two Years before Current Fiscal Year	434.3	291.2
Financing Receivable, Originated Three Years before Current Fiscal Year	209.9	162.8
Financing Receivable, Originated Four Years before Current Fiscal Year	116.2	161.8
Financed Receivables, By Origination Year, Prior	172.9	125.2
Finance Receivables, Total	2,304.1	2,330.8
Dealer | Retail | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	1.0
Financing Receivable, Originated One Year before Current Fiscal Year	25.0
Financing Receivable, Originated Two Years before Current Fiscal Year	6.7
Financing Receivable, Originated Three Years before Current Fiscal Year	2.4
Financing Receivable, Originated Four Years before Current Fiscal Year	5.7
Financed Receivables, By Origination Year, Prior	0.7
Finance Receivables, Total	41.5
Customer Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	3,984.6	5,153.2
Financing Receivable, Originated One Year before Current Fiscal Year	4,030.9	3,067.6
Financing Receivable, Originated Two Years before Current Fiscal Year	2,269.0	1,596.8
Financing Receivable, Originated Three Years before Current Fiscal Year	1,058.3	875.4
Financing Receivable, Originated Four Years before Current Fiscal Year	476.9	282.5
Financed Receivables, By Origination Year, Prior	132.2	74.1
Finance Receivables, Total	11,951.9	11,049.6
Customer Retail | Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year		1.5
Financing Receivable, Originated One Year before Current Fiscal Year		10.5
Financing Receivable, Originated Two Years before Current Fiscal Year		6.6
Financing Receivable, Originated Three Years before Current Fiscal Year		4.7
Financing Receivable, Originated Four Years before Current Fiscal Year		4.2
Financed Receivables, By Origination Year, Prior		0.9
Finance Receivables, Total		28.4
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	3,565.1	4,689.7
Financing Receivable, Originated One Year before Current Fiscal Year	3,668.3	2,730.2
Financing Receivable, Originated Two Years before Current Fiscal Year	2,019.1	1,329.9
Financing Receivable, Originated Three Years before Current Fiscal Year	884.1	730.5
Financing Receivable, Originated Four Years before Current Fiscal Year	399.6	229.2
Financed Receivables, By Origination Year, Prior	111.8	65.1
Finance Receivables, Total	10,648.0	9,774.6
Customer Retail | Fleet | Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	0.9	1.0
Financing Receivable, Originated One Year before Current Fiscal Year	10.6	9.4
Financing Receivable, Originated Two Years before Current Fiscal Year	8.9	5.1
Financing Receivable, Originated Three Years before Current Fiscal Year	5.2	4.2
Financing Receivable, Originated Four Years before Current Fiscal Year	2.4	4.2
Financed Receivables, By Origination Year, Prior	5.2	0.6
Finance Receivables, Total	33.2	24.5
Customer Retail | Fleet | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	3,526.3	4,601.7
Financing Receivable, Originated One Year before Current Fiscal Year	3,509.3	2,667.2
Financing Receivable, Originated Two Years before Current Fiscal Year	1,921.9	1,309.5
Financing Receivable, Originated Three Years before Current Fiscal Year	829.7	719.2
Financing Receivable, Originated Four Years before Current Fiscal Year	389.1	226.7
Financed Receivables, By Origination Year, Prior	107.8	64.1
Finance Receivables, Total	10,284.1	9,588.4
Customer Retail | Fleet | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	19.1	46.0
Financing Receivable, Originated One Year before Current Fiscal Year	41.0	32.0
Financing Receivable, Originated Two Years before Current Fiscal Year	14.1	7.5
Financing Receivable, Originated Three Years before Current Fiscal Year	9.4	5.7
Financing Receivable, Originated Four Years before Current Fiscal Year	3.0	1.3
Financed Receivables, By Origination Year, Prior	0.6	0.9
Finance Receivables, Total	87.2	93.4
Customer Retail | Fleet | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	19.7	42.0
Financing Receivable, Originated One Year before Current Fiscal Year	118.0	31.0
Financing Receivable, Originated Two Years before Current Fiscal Year	83.1	12.9
Financing Receivable, Originated Three Years before Current Fiscal Year	45.0	5.6
Financing Receivable, Originated Four Years before Current Fiscal Year	7.5	1.2
Financed Receivables, By Origination Year, Prior	3.4	0.1
Finance Receivables, Total	276.7	92.8
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	419.5	463.5
Financing Receivable, Originated One Year before Current Fiscal Year	362.6	337.4
Financing Receivable, Originated Two Years before Current Fiscal Year	249.9	266.9
Financing Receivable, Originated Three Years before Current Fiscal Year	174.2	144.9
Financing Receivable, Originated Four Years before Current Fiscal Year	77.3	53.3
Financed Receivables, By Origination Year, Prior	20.4	9.0
Finance Receivables, Total	1,303.9	1,275.0
Customer Retail | Owner/Operator | Charge Offs Of Finance Receivables
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	0.2	0.5
Financing Receivable, Originated One Year before Current Fiscal Year	1.3	1.1
Financing Receivable, Originated Two Years before Current Fiscal Year	2.2	1.5
Financing Receivable, Originated Three Years before Current Fiscal Year	0.8	0.5
Financing Receivable, Originated Four Years before Current Fiscal Year	0.7
Financed Receivables, By Origination Year, Prior	0.5	0.3
Finance Receivables, Total	5.7	3.9
Customer Retail | Owner/Operator | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	416.3	460.9
Financing Receivable, Originated One Year before Current Fiscal Year	348.0	332.9
Financing Receivable, Originated Two Years before Current Fiscal Year	237.8	263.6
Financing Receivable, Originated Three Years before Current Fiscal Year	168.7	142.1
Financing Receivable, Originated Four Years before Current Fiscal Year	73.9	52.8
Financed Receivables, By Origination Year, Prior	20.0	8.6
Finance Receivables, Total	1,264.7	1,260.9
Customer Retail | Owner/Operator | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	3.1	2.0
Financing Receivable, Originated One Year before Current Fiscal Year	12.6	3.2
Financing Receivable, Originated Two Years before Current Fiscal Year	9.6	2.2
Financing Receivable, Originated Three Years before Current Fiscal Year	4.1	1.3
Financing Receivable, Originated Four Years before Current Fiscal Year	2.0	0.3
Financed Receivables, By Origination Year, Prior	0.3
Finance Receivables, Total	31.7	9.0
Customer Retail | Owner/Operator | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable Originated In Current Fiscal Year	0.1	0.6
Financing Receivable, Originated One Year before Current Fiscal Year	2.0	1.3
Financing Receivable, Originated Two Years before Current Fiscal Year	2.5	1.1
Financing Receivable, Originated Three Years before Current Fiscal Year	1.4	1.5
Financing Receivable, Originated Four Years before Current Fiscal Year	1.4	0.2
Financed Receivables, By Origination Year, Prior	0.1	0.4
Finance Receivables, Total	$ 7.5	$ 5.1