Summary of Impaired Loans and Specific Reserve (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 49.2		$ 54.3
Associated allowance	(11.8)		(10.7)
Net carrying amount of impaired loans	37.4		43.6
Average recorded investment	53.7	[1]	61.2	[2]
Dealer wholesale financing
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	3.7		3.6
Associated allowance	(2.2)		(2.2)
Net carrying amount of impaired loans	1.5		1.4
Average recorded investment	6.3	[1]	17.9	[2]
Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	39.6		43.9
Associated allowance	(8.4)		(7.3)
Net carrying amount of impaired loans	31.2		36.6
Average recorded investment	39.3	[1]	31.9	[2]
Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	5.9		6.8
Associated allowance	(1.2)		(1.2)
Net carrying amount of impaired loans	4.7		5.6
Average recorded investment	$ 8.1	[1]	$ 11.4	[2]

[1] Represents the average during the 12 months ended March 31, 2013.

[2] Represents the average during the 12 months ended March 31, 2012.