Derivative Instruments and Risk Management - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Maximum [Member]
Derivative [Line Items]
Maturity period of foreign currency forward exchange contracts	12 months
Not Designated as Hedging Instrument [Member] | Foreign Currency Forward Exchange Contracts [Member] | Other net income/(expense) [Member]
Derivative [Line Items]
Amount of gain/(loss) recognized in income	$ (1.6)	$ (0.6)
Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Accumulated Other Comprehensive Loss [Member]
Derivative [Line Items]
Amount of gain/(loss) recognized in income	$ 1.2	$ 0.2