Finance Receivables Summary by those Evaluated Collectively and Individually (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	$ 108.0	$ 114.4
Allowance for finance receivables determined individually	25.9	27.9
Recorded investment for finance receivables evaluated collectively	7,658.4	7,173.3
Allowance for finance receivables determined collectively	115.4	111.1
Dealer wholesale financing
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	18.1	18.4
Allowance for finance receivables determined individually	2.8	2.2
Recorded investment for finance receivables evaluated collectively	1,787.8	1,498.7
Allowance for finance receivables determined collectively	11.8	9.5
Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Recorded investment for impaired finance receivables evaluated individually	89.9	96.0
Allowance for finance receivables determined individually	23.1	25.7
Recorded investment for finance receivables evaluated collectively	5,870.6	5,674.6
Allowance for finance receivables determined collectively	$ 103.6	$ 101.6