| Significant Accounting Policies - Summary of Changes in Warranty Provision (Parenthetical) (Detail) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | 
|---|---|---|
| Product Warranty Liability [Line Items] | ||
| Standard product warranty provision | $ 27 | $ 61 | 
| Maximum [Member] | ||
| Product Warranty Liability [Line Items] | ||
| Standard product warranty provision | $ 1 | 
| X | ||||||||||
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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| X | ||||||||||
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- Definition Amount as of the balance sheet date of the aggregate standard product warranty liability. Does not include the balance for the extended product warranty liability. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Details 
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