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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

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