Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998890-113959

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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- Definition

The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- Definition

Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

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- Definition

Derivative maturity date range.

+ References

No definition available.

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- Definition

Derivative, Maturity Month and Year

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Derivatives - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
Derivatives - Additional Information (Detail) - USD ($)	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Foreign Currency Forward Contracts \| Cash Flow Hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value of derivatives	$ 36,800,000		$ 36,800,000
Contract maturity period			One year or less
Contract expiring terms			2019-06
Maximum length of time hedged in cash flow hedge			12 months
Pre-tax gain to be reclassified into earnings within the next 12 months	3,000		$ 3,000
Foreign Exchange Forward And Option Contracts [Member] \| Not Designated as Hedging Instrument, Economic Hedge [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value of derivatives	12,000,000		$ 12,000,000
Contract expiring terms			2018-11
Losses from foreign currency forward and option contracts not designated as hedging instruments	$ (108,000)	$ (502,000)	$ (299,000)	$ (912,000)