Summary of Impaired Loans (Detail) - Financial Services - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 14.0	$ 18.0
Associated allowance	(2.7)	(3.4)
Net carrying amount of impaired loans with specific reserve	11.3	14.6
Impaired loans with no specific reserve	9.4	7.7
Net carrying amount of impaired loans	20.7	22.3
Average recorded investment	27.3	35.4
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve		0.1
Associated allowance		(0.1)
Average recorded investment	4.9	0.1
Dealer | Retail
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserve	2.3	2.5
Net carrying amount of impaired loans	2.3	2.5
Average recorded investment	2.4	3.2
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	10.9	14.5
Associated allowance	(2.1)	(2.3)
Net carrying amount of impaired loans with specific reserve	8.8	12.2
Impaired loans with no specific reserve	6.7	4.9
Net carrying amount of impaired loans	15.5	17.1
Average recorded investment	16.6	29.3
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	3.1	3.4
Associated allowance	(0.6)	(1.0)
Net carrying amount of impaired loans with specific reserve	2.5	2.4
Impaired loans with no specific reserve	0.4	0.3
Net carrying amount of impaired loans	2.9	2.7
Average recorded investment	$ 3.4	$ 2.8