Summary of Impaired Loans and Specific Reserve (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 15.8	$ 22.4
Associated allowance	(2.5)	(4.1)
Net carrying amount of impaired loans	13.3	18.3
Average recorded investment	34.1	39.7
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	0.5	8.5
Associated allowance	(0.5)	(1.4)
Net carrying amount of impaired loans		7.1
Average recorded investment	8.8	5.8
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	12.7	10.8
Associated allowance	(1.5)	(2.1)
Net carrying amount of impaired loans	11.2	8.7
Average recorded investment	22.5	28.9
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	2.6	3.1
Associated allowance	(0.5)	(0.6)
Net carrying amount of impaired loans	2.1	2.5
Average recorded investment	$ 2.8	$ 5.0