Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 9,476.3	$ 8,797.7
Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	9,346.8	8,710.8
Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	75.9	29.5
At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	53.6	57.4
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,910.6	1,528.5
Dealer | Wholesale | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,905.6	1,519.3
Dealer | Wholesale | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4.9	9.1
Dealer | Wholesale | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	0.1	0.1
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,331.1	1,406.0
Dealer | Retail | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,327.0	1,406.0
Dealer | Retail | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	0.0	0.0
Dealer | Retail | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4.1	0.0
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5,023.6	4,928.7
Customer Retail | Fleet | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,916.7	4,863.4
Customer Retail | Fleet | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	64.8	14.9
Customer Retail | Fleet | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	42.1	50.4
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,211.0	934.5
Customer Retail | Owner/Operator | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,197.5	922.1
Customer Retail | Owner/Operator | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6.2	5.5
Customer Retail | Owner/Operator | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 7.3	$ 6.9