Deferred Income Tax Assets (liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Notes and accounts receivable	$ 0	$ 3
Stock-based compensation	1,339	1,104
Allowance for sales return	324	541
Inventory reserve	1,925	1,733
Foreign currency translation	47	(20)
Property and equipment	(483)	(359)
Investment tax credits	4,512	4,532
Net operating loss carryforwards	16,754	14,028
Others	1,013	494
Valuation allowance	(20,816)	(18,108)
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	$ 4,615	$ 3,948

Deferred Tax Assets Accounts Receivable and Advance Payments

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Deferred tax assets (liabilities), property, plant and equipment.

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Deferred Tax Assets, Unrealized Currency Exchange Loss (Gain)

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax credit carryforwards, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from estimated returns and sales allowances.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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