Summary of Impaired Loans and Specific Reserve (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserve	$ 54.0				$ 57.8
Associated allowance	(12.4)				(10.8)
Net carrying amount of impaired loans	41.6				47.0
Average recorded investment	46.7	[1]	57.7	[1]
Dealer wholesale financing
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserve	3.3				18.4
Associated allowance	(2.2)				(2.2)
Net carrying amount of impaired loans	1.1				16.2
Average recorded investment	12.9	[1]	11.7	[1]
Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserve	42.4				27.9
Associated allowance	(8.5)				(6.0)
Net carrying amount of impaired loans	33.9				21.9
Average recorded investment	23.6	[1]	30.9	[1]
Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with specific reserve	8.3				11.5
Associated allowance	(1.7)				(2.6)
Net carrying amount of impaired loans	6.6				8.9
Average recorded investment	$ 10.2	[1]	$ 15.1	[1]

[1] Represents the average during the 12 months ended September 30, 2012 and 2011.