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Basis of Presentation and Summary of Significant Accounting Policies - Foreign Currency Transactions and Translation (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Foreign Currency Translation [Line Items] |  |  |
Foreign currency exchange loss, net | $ (3,940,000) | $ (1,151,000) | $ (1,023,000)
Minimum |  |  |
Foreign Currency Translation [Line Items] |  |  |
Forward contracts terms | 30 days |  |
Maximum |  |  |
Foreign Currency Translation [Line Items] |  |  |
Forward contracts terms | 210 days |  |
Forward Contracts |  |  |
Foreign Currency Translation [Line Items] |  |  |
Notional amounts of pen forward contracts | $ 58,400,000 | $ 27,100,000 |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30700-110894 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30690-110894 + Details
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