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Summary of the Changes in Allowance for Doubtful Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Receivables [Abstract]      
Balance at beginning of year $ 3 $ 5 $ 12
Additions: Bad debt expense 5 24 23
Less: Write-off (7) (26) (29)
Translation adjustment     (1)
Balance at end of year $ 1 $ 3 $ 5