Financing Receivables by Aging Category (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	$ 7,659.7	$ 7,177.0
31 - 60 days past due	30.8	29.7
Greater than 60 days past due	75.9	81.0
Financing Receivables	7,766.4	7,287.7
Dealer wholesale financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,786.3	1,490.0
31 - 60 days past due	1.5	9.1
Greater than 60 days past due	18.1	17.9
Financing Receivables	1,805.9	1,517.0
Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	4,500.2	4,321.8
31 - 60 days past due	17.7	8.7
Greater than 60 days past due	42.7	46.0
Financing Receivables	4,560.6	4,376.5
Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,373.2	1,365.2
31 - 60 days past due	11.6	11.9
Greater than 60 days past due	15.1	17.1
Financing Receivables	$ 1,399.9	$ 1,394.2