Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 8,707.7	$ 8,316.3
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8,569.6	8,146.4
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	79.6	98.8
Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	58.5	71.1
Dealer wholesale financing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,736.2	1,541.0
Dealer wholesale financing | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,681.4	1,479.1
Dealer wholesale financing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	45.7	58.3
Dealer wholesale financing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	9.1	3.6
Retail | Dealer
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,403.3	1,429.7
Retail | Dealer | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,396.3	1,423.3
Retail | Dealer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	7.0	6.3
Retail | Dealer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables		0.1
Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,294.6	3,956.6
Retail | Fleet | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,235.2	3,878.4
Retail | Fleet | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	20.0	23.5
Retail | Fleet | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	39.4	54.7
Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,273.6	1,389.0
Retail | Owner/Operator | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,256.7	1,365.6
Retail | Owner/Operator | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	6.9	10.7
Retail | Owner/Operator | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 10.0	$ 12.7