Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_RestructuringCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Restructuring and Severance - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Feb. 14, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses		$ 223	$ (49)	$ 591	$ (49)
3VR
Restructuring Cost And Reserve [Line Items]
Date of acquisition completed	Feb. 14, 2018
Restructuring and severance expenses		200		600
3VR \| Facility Rental
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses		100		300
3VR \| Severance
Restructuring Cost And Reserve [Line Items]
Restructuring and severance expenses		$ 100		$ 300