Financing Receivables by Aging Category (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	$ 8,649.6	$ 8,270.5
31 - 60 days past due	28.3	17.8
Greater than 60 days past due	29.8	28.0
Financing Receivables	8,707.7	8,316.3
Dealer wholesale financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,727.8	1,537.0
31 - 60 days past due	1.8	0.5
Greater than 60 days past due	6.6	3.5
Financing Receivables	1,736.2	1,541.0
Retail | Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,403.3	1,429.7
Financing Receivables	1,403.3	1,429.7
Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	4,259.3	3,934.8
31 - 60 days past due	20.9	9.4
Greater than 60 days past due	14.4	12.4
Financing Receivables	4,294.6	3,956.6
Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,259.2	1,369.0
31 - 60 days past due	5.6	7.9
Greater than 60 days past due	8.8	12.1
Financing Receivables	$ 1,273.6	$ 1,389.0