Summary of Impaired Loans and Specific Reserve (Detail) - Financial Services - USD ($) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015		Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 22.6		$ 15.8
Associated allowance	(3.4)		(2.5)
Net carrying amount of impaired loans	19.2		13.3
Average recorded investment	35.7	[1]	33.7	[2]
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	4.7		0.5
Associated allowance	(0.5)		(0.5)
Net carrying amount of impaired loans	4.2
Average recorded investment	6.6	[1]	8.9	[2]
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	16.2		12.7
Associated allowance	(2.5)		(1.5)
Net carrying amount of impaired loans	13.7		11.2
Average recorded investment	26.8	[1]	21.6	[2]
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	1.7		2.6
Associated allowance	(0.4)		(0.5)
Net carrying amount of impaired loans	1.3		2.1
Average recorded investment	$ 2.3	[1]	$ 3.2	[2]

[1] Represents the average during the 12 months ended September 30, 2015.

[2] Represents the average during the 12 months ended September 30, 2014.