Financial Derivatives and Hedging Activities - Fair Values of Derivative Instruments (Detail) - Forward Foreign Currency Exchange Contracts [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Designated as Hedging [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Derivative asset, fair value	$ 1,489	$ 1,066
Designated as Hedging [Member] \| Other Current Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative liability, fair value	522	4,787
Not Designated as Hedging [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Derivative asset, fair value	203	151
Not Designated as Hedging [Member] \| Other Current Liabilities [Member]
Derivatives Fair Value [Line Items]
Derivative liability, fair value	$ 309	$ 43

Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226006-175313

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant