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
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Derivatives	$ 0.8	$ 1.3
Hedged term notes	(0.4)	(1.3)
Total income and expense	$ 0.4	$ 0.0