Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 8,265.8	$ 8,316.3
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8,089.5	8,146.4
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	104.3	98.8
Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	72.0	71.1
Dealer wholesale financing
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,526.0	1,541.0
Dealer wholesale financing | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,467.4	1,479.1
Dealer wholesale financing | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	54.9	58.3
Dealer wholesale financing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	3.7	3.6
Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,009.5	3,956.6
Retail | Fleet | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	3,921.8	3,878.4
Retail | Fleet | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	31.5	23.5
Retail | Fleet | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	56.2	54.7
Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,342.3	1,389.0
Retail | Owner/Operator | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,317.7	1,365.6
Retail | Owner/Operator | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	12.5	10.7
Retail | Owner/Operator | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	12.1	12.7
Retail | Dealer
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,388.0	1,429.7
Retail | Dealer | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,382.6	1,423.3
Retail | Dealer | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	5.4	6.3
Retail | Dealer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables		$ 0.1