Financing Receivables by Aging Category (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	$ 8,210.1	$ 8,270.5
31 - 60 days past due	23.0	17.8
Greater than 60 days past due	32.7	28.0
Financing Receivables	8,265.8	8,316.3
Dealer wholesale financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,520.2	1,537.0
31 - 60 days past due	1.9	0.5
Greater than 60 days past due	3.9	3.5
Financing Receivables	1,526.0	1,541.0
Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	3,980.8	3,934.8
31 - 60 days past due	11.8	9.4
Greater than 60 days past due	16.9	12.4
Financing Receivables	4,009.5	3,956.6
Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,321.1	1,369.0
31 - 60 days past due	9.3	7.9
Greater than 60 days past due	11.9	12.1
Financing Receivables	1,342.3	1,389.0
Retail | Dealer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,388.0	1,429.7
Financing Receivables	$ 1,388.0	$ 1,429.7