Summary of Impaired Loans (Detail) - Financial Services - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2019		Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 15.4		$ 18.0
Associated allowance	(2.7)		(3.4)
Net carrying amount of impaired loans with specific reserve	12.7		14.6
Impaired loans with no specific reserve	6.2		7.7
Net carrying amount of impaired loans	18.9		22.3
Average recorded investment	27.2	[1]	38.7	[2]
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve			0.1
Associated allowance			(0.1)
Average recorded investment	0.1	[1]	0.1	[2]
Dealer | Retail
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserve	2.5		2.5
Net carrying amount of impaired loans	2.5		2.5
Average recorded investment	2.6	[1]	3.8	[2]
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	12.7		14.5
Associated allowance	(2.1)		(2.3)
Net carrying amount of impaired loans with specific reserve	10.6		12.2
Impaired loans with no specific reserve	3.4		4.9
Net carrying amount of impaired loans	14.0		17.1
Average recorded investment	21.2	[1]	32.8	[2]
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	2.7		3.4
Associated allowance	(0.6)		(1.0)
Net carrying amount of impaired loans with specific reserve	2.1		2.4
Impaired loans with no specific reserve	0.3		0.3
Net carrying amount of impaired loans	2.4		2.7
Average recorded investment	$ 3.3	[1]	$ 2.0	[2]

[1] Represents the average during the 12 months ended June 30, 2019.

[2] Represents the average during the 12 months ended June 30, 2018.