Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 8,160.6	$ 7,287.7
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8,004.1	7,075.7
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	70.3	97.6
Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	86.2	114.4
Dealer wholesale financing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,702.4	1,517.0
Dealer wholesale financing | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,663.8	1,451.9
Dealer wholesale financing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	35.3	46.7
Dealer wholesale financing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	3.3	18.4
Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5,075.1	4,376.5
Retail | Fleet | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,984.4	4,262.8
Retail | Fleet | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	21.9	37.2
Retail | Fleet | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	68.8	76.5
Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,383.1	1,394.2
Retail | Owner/Operator | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,355.9	1,361.0
Retail | Owner/Operator | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	13.1	13.7
Retail | Owner/Operator | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 14.1	$ 19.5