Finance Receivables Summary by those Evaluated Collectively and Individually (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	$ 46.2	$ 50.6
Allowance for impaired finance receivables determined individually	5.9	7.3
Recorded investment for finance receivables evaluated collectively	8,834.9	8,769.5
Allowance for finance receivables determined collectively	116.5	114.0
Dealer | Wholesale
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	6.5	8.5
Allowance for impaired finance receivables determined individually	1.3	1.4
Recorded investment for finance receivables evaluated collectively	1,672.7	1,608.0
Allowance for finance receivables determined collectively	9.5	9.0
Dealer | Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for finance receivables evaluated collectively	1,464.3	1,525.6
Allowance for finance receivables determined collectively	12.9	13.4
Customer Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	39.7	42.1
Allowance for impaired finance receivables determined individually	4.6	5.9
Recorded investment for finance receivables evaluated collectively	5,697.9	5,635.9
Allowance for finance receivables determined collectively	$ 94.1	$ 91.6