Amortized Cost Basis of Impaired Loans and Specific Reserve (Detail) - Financial Services - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020		Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	$ 29.0		$ 14.0
Associated allowance	(2.7)		(2.7)
Net carrying amount of impaired loans with specific reserve	26.3		11.3
Impaired loans with no specific reserve	8.7		9.4
Net carrying amount of impaired loans	35.0		20.7
Average amortized cost basis	29.9	[1]	32.6	[2]
Dealer | Wholesale
Financing Receivable, Impaired [Line Items]
Average amortized cost basis	4.9	[1]	0.1	[2]
Dealer | Retail
Financing Receivable, Impaired [Line Items]
Impaired loans with no specific reserve	1.7		2.3
Net carrying amount of impaired loans	1.7		2.3
Average amortized cost basis	2.3	[1]	2.9	[2]
Customer Retail | Fleet
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	26.7		10.9
Associated allowance	(2.2)		(2.1)
Net carrying amount of impaired loans with specific reserve	24.5		8.8
Impaired loans with no specific reserve	6.7		6.7
Net carrying amount of impaired loans	31.2		15.5
Average amortized cost basis	19.5	[1]	26.3	[2]
Customer Retail | Owner/Operator
Financing Receivable, Impaired [Line Items]
Impaired loans with a specific reserve	2.3		3.1
Associated allowance	(0.5)		(0.6)
Net carrying amount of impaired loans with specific reserve	1.8		2.5
Impaired loans with no specific reserve	0.3		0.4
Net carrying amount of impaired loans	2.1		2.9
Average amortized cost basis	$ 3.2	[1]	$ 3.3	[2]

[1] Represents the average during the 12 months ended March 31, 2020.

[2] Represents the average during the 12 months ended March 31, 2019.