Summary of Impaired Loans (Cash Basis Method) (Detail) - Financial Services - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income recognized:
Interest income recognized on a cash basis	$ 1.7	$ 1.5	$ 1.8
Customer Retail | Fleet
Interest income recognized:
Interest income recognized on a cash basis	1.6	1.1	1.4
Customer Retail | Owner/Operator
Interest income recognized:
Interest income recognized on a cash basis	$ 0.1	$ 0.4	$ 0.4