Summary of Impaired Loans (Detail) - Financial Services - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 20.8	$ 29.1
Associated allowance	(3.2)	(4.3)
Net carrying amount of impaired loans with specific reserve	17.6	24.8
Impaired loans with no specific reserve	11.0	6.8
Net carrying amount of impaired loans	28.6	31.6
Average recorded investment	33.2	33.5
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	0.1	5.0
Associated allowance	(0.1)	(0.3)
Net carrying amount of impaired loans with specific reserve	0.0	4.7
Impaired loans with no specific reserve	0.0	0.0
Net carrying amount of impaired loans	0.0	4.7
Average recorded investment	2.8	4.4
Dealer | Retail
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	0.0	0.0
Associated allowance	0.0	0.0
Net carrying amount of impaired loans with specific reserve	0.0	0.0
Impaired loans with no specific reserve	0.0	0.0
Net carrying amount of impaired loans	0.0	0.0
Average recorded investment	0.0	0.0
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	18.9	21.7
Associated allowance	(2.8)	(3.5)
Net carrying amount of impaired loans with specific reserve	16.1	18.2
Impaired loans with no specific reserve	10.8	6.5
Net carrying amount of impaired loans	26.9	24.7
Average recorded investment	28.0	26.6
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	1.8	2.4
Associated allowance	(0.3)	(0.5)
Net carrying amount of impaired loans with specific reserve	1.5	1.9
Impaired loans with no specific reserve	0.2	0.3
Net carrying amount of impaired loans	1.7	2.2
Average recorded investment	$ 2.4	$ 2.5