Finance and Other Receivables - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended												3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Financial Services	Dec. 31, 2012 Financial Services	Mar. 31, 2013 Financial Services Dealer wholesale financing	Dec. 31, 2012 Financial Services Dealer wholesale financing	Mar. 31, 2013 Financial Services Retail Fleet	Dec. 31, 2012 Financial Services Retail Fleet	Mar. 31, 2013 Financial Services Retail Fleet Post-modification	Mar. 31, 2012 Financial Services Retail Fleet Post-modification	Mar. 31, 2013 Financial Services Retail Owner/Operator	Dec. 31, 2012 Financial Services Retail Owner/Operator	Mar. 31, 2013 Financial Services Retail Owner/Operator Post-modification	Mar. 31, 2012 Financial Services Retail Owner/Operator Post-modification	Dec. 31, 2012 Financial Services Retail Dealer	Mar. 31, 2013 Financial Services Minimum Loans Receivable	Mar. 31, 2013 Financial Services Maximum Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modifications extended contractual terms				4 months	7 months
Receivable, collection period																	36 months	60 months
Recorded investment of finance receivables that are on non-accrual status						$ 3.1	$ 3.1	$ 46.6	$ 42.8			$ 10.3	$ 11.7			$ 0.1
Impaired Loans	5.5		6.8
Percentage of portfolio	4.00%
Loans accounted for as troubled debt restructurings				37.8	38.5
Recorded Investment, subsequently defaulted										0.5	0.9			0.1	0.1
Repossessed inventory	11.5		20.9
Proceeds from the sales of repossessed assets	$ 20.3	$ 16.2