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Derivatives - Summary of Primary Net Hedging Positions and Corresponding Fair Values (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | $ 208,922 | $ 120,208
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | (6,030) | 2,442
Forward Exchange Contracts [Member] | U.S. Dollar/Japanese Yen [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 70,175 | 30,522
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | (233) | 763
Forward Exchange Contracts [Member] | U.S. Dollar/South Korean Won [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 79,672 | 50,049
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | (3,799) | 1,342
Forward Exchange Contracts [Member] | U.S. Dollar/Euro [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 26,140 | 18,040
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | (1,047) | 156
Forward Exchange Contracts [Member] | U.S. Dollar/U.K. Pound Sterling [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 12,104 | 6,067
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | (337) | 117
Forward Exchange Contracts [Member] | U.S. Dollar/Taiwan Dollar [Member] |  |
Derivative [Line Items] |  |
Currency Hedged (Buy/Sell), Gross Notional Value, Net | 20,831 | 15,530
Currency Hedged (Buy/Sell), Fair Value, (Liability)/Asset, Net | $ (614) | $ 64

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