Financing Receivables by Aging Category (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	$ 8,094.2	$ 7,177.0
31 - 60 days past due	19.2	29.7
Greater than 60 days past due	47.2	81.0
Financing Receivables	8,160.6	7,287.7
Dealer wholesale financing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,697.3	1,490.0
31 - 60 days past due	1.3	9.1
Greater than 60 days past due	3.8	17.9
Financing Receivables	1,702.4	1,517.0
Retail | Fleet
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	5,037.5	4,321.8
31 - 60 days past due	7.2	8.7
Greater than 60 days past due	30.4	46.0
Financing Receivables	5,075.1	4,376.5
Retail | Owner/Operator
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current and up to 30 days past due	1,359.4	1,365.2
31 - 60 days past due	10.7	11.9
Greater than 60 days past due	13.0	17.1
Financing Receivables	$ 1,383.1	$ 1,394.2