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Fair Value Measurements - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value Measurements [Line Items]      
Assets measured at fair value on a recurring basis $ 0 $ 0  
Liabilities measured at fair value on a recurring basis 0 0  
Fair value hierarchy transfers amount 0 0 $ 0
Assets measured at fair value on a non-recurring basis 0 0  
Liabilities measured at fair value on a non-recurring basis $ 0 $ 0  
Foreign currency forward contracts | Other income, net      
Fair Value Measurements [Line Items]      
Net gain on foreign currency forward contracts     $ 500,000