Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) - Financial Services - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 9,160.7	$ 8,797.7
Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	9,015.6	8,710.8
Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	85.4	29.5
At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	59.7	57.4
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,764.0	1,528.5
Dealer | Wholesale | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,757.9	1,519.3
Dealer | Wholesale | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6.0	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	1,286.0	1,406.0
Dealer | Retail | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,282.1	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	3.9	0.0
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5,139.4	4,928.7
Customer Retail | Fleet | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5,019.1	4,863.4
Customer Retail | Fleet | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	71.4	14.9
Customer Retail | Fleet | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	48.9	50.4
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	971.3	934.5
Customer Retail | Owner/Operator | Performing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	956.5	922.1
Customer Retail | Owner/Operator | Watch
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8.0	5.5
Customer Retail | Owner/Operator | At-risk
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 6.8	$ 6.9