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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative [Line Items]
Derivatives	$ 0.3	$ (0.7)	$ 1.1	$ 0.6
Hedged term notes	0.2	0.9	(0.2)	(0.4)
Total income and expense	$ 0.5	$ 0.2	$ 0.9	$ 0.2