Location and Amount of (Income)/Expense for the Cash Flow and Fair Value Hedges Recognized in Statement of Comprehensive Income (Detail) - Financial Services - (Gain)/loss on fair value hedges - Interest-Rate Contracts - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Derivatives	$ 0.0	$ 0.4	$ 1.1	$ 1.0
Hedged term notes	0.4	(0.2)	0.2	(0.6)
Total income and expense	$ 0.4	$ 0.2	$ 1.3	$ 0.4