Derivatives and Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Gain (Loss) on Derivative Used in Net Investment Hedge, Net of Tax	$ (29.6)	$ 44.2
Cross Currency Interest Rate Contract [Member]
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Derivative Liability, Notional Amount	$ 481.4
Derivative, Notional Amount		$ 475.6