Beginning Balance, Annual Activity and Ending Balance of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 320,231	$ 314,158	$ 305,314		$ 305,314
Foreign currency translation adjustment	638	(898)	672	$ (67)	412	$ 970
Balance	328,624	320,231	314,158		328,624
Accumulated Foreign Currency Adjustment Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(4,733)	(3,835)	(4,507)		(4,507)
Foreign currency translation adjustment	638	(898)	672
Balance	$ (4,095)	$ (4,733)	$ (3,835)		$ (4,095)

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4I
-URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant