Derivatives and Financial Instruments - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Impaired Assets to be Disposed of by Method Other than Sale, Carrying Value of Asset		$ 0
Debt, Long-term and Short-term, Combined Amount	$ 1,503,400,000	4,279,200,000
Gain (Loss) on Derivative Used in Net Investment Hedge, Net of Tax	(22,500,000)	44,200,000
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 410,400,000	$ 475,600,000