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Financial Instruments - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Derivative [Line Items]    
Estimated amount of net foreign currency derivative gains in other comprehensive income reclassified to earnings within 12 months $ 1,900,000  
Foreign exchange contracts [Member]    
Derivative [Line Items]    
Notional amount of foreign currency derivative hedges 304,300,000  
Cash flow hedge [Member]    
Derivative [Line Items]    
Net gains recognized in OCI $ 4,300,000 $ 2,100,000