Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Net settlement payable	$ 4,800,000
Estimated amount of net foreign currency derivative losses in other comprehensive income reclassified to earnings within 12 months	$ (3,000,000)
Minimum [Member]
Derivative [Line Items]
Foreign exchange contracts period	12 months
Maximum [Member]
Derivative [Line Items]
Foreign exchange contracts period	15 months
Foreign exchange contracts [Member]
Derivative [Line Items]
Notional amount of foreign currency derivative hedges	$ 282,800,000
Cash flow hedge [Member]
Derivative [Line Items]
Net losses recognized in OCI	(1,800,000)	$ (6,700,000)
Cash flow hedge [Member] | Foreign exchange contracts [Member]
Derivative [Line Items]
Estimated amount of net foreign currency derivative losses in other comprehensive income reclassified to earnings within 12 months	$ (3,000,000)