Allowance for Credit Losses (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		$ 60.7	[1]	$ 58.4
Provision (benefit) for losses		2.9		1.2
Charge-offs		(1.2)		(2.0)
Recoveries		0.6		0.6
Ending Balance		63.0		58.2
Dealer | Wholesale
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		3.1		2.4
Provision (benefit) for losses		0.1		0.2
Charge-offs
Recoveries
Ending Balance		3.2		2.6
Dealer | Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		8.4		7.9
Provision (benefit) for losses		(0.1)
Charge-offs
Recoveries
Ending Balance		8.3		7.9
Customer Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance		47.7		46.9
Provision (benefit) for losses		2.5		0.4
Charge-offs		(1.0)		(2.0)
Recoveries		0.6		0.6
Ending Balance		49.8		45.9
Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning Balance	[2]	1.5		1.2
Provision (benefit) for losses	[2]	0.4		0.6
Charge-offs	[2]	(0.2)
Recoveries	[2]
Ending Balance	[2]	$ 1.7		$ 1.8

[1] The December 31, 2018 balance sheet has been derived from audited financial statements.

[2] Operating lease and other trade receivables