Summary of Impaired Loans and Specific Reserve (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 34.2		$ 54.3
Associated allowance	(5.2)		(10.7)
Net carrying amount of impaired loans	29.0		43.6
Average recorded investment	42.2	[1]	55.6	[2]
Dealer wholesale financing
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	9.1		3.6
Associated allowance	(1.5)		(2.2)
Net carrying amount of impaired loans	7.6		1.4
Average recorded investment	4.8	[1]	12.7	[2]
Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	20.9		43.9
Associated allowance	(2.9)		(7.3)
Net carrying amount of impaired loans	18.0		36.6
Average recorded investment	31.4	[1]	32.7	[2]
Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	4.2		6.8
Associated allowance	(0.8)		(1.2)
Net carrying amount of impaired loans	3.4		5.6
Average recorded investment	$ 6.0	[1]	$ 10.2	[2]

[1] Represents the average during the 12 months ended September 30, 2013.

[2] Represents the average during the 12 months ended September 30, 2012.