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Derivatives - Summary of Primary Net Hedging Positions and Corresponding Fair Values (Detail) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
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Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | $ 149,088 | $ 208,922
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | 3,091 | (6,030)
Forward Exchange Contracts [Member] | U.S. Dollar/Japanese Yen [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 40,004 | 70,175
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | 1,143 | (233)
Forward Exchange Contracts [Member] | U.S. Dollar/South Korean Won [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 56,628 | 79,672
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | 759 | (3,799)
Forward Exchange Contracts [Member] | U.S. Dollar/Euro [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 23,678 | 26,140
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | 612 | (1,047)
Forward Exchange Contracts [Member] | U.S. Dollar/U.K. Pound Sterling [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 10,001 | 12,104
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | 314 | (337)
Forward Exchange Contracts [Member] | U.S. Dollar/Taiwan Dollar [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 18,777 | 20,831
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | $ 263 | $ (614)

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