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Accounts Receivable and Sales Concentrations - Summary of Activity in the Allowance for Doubtful Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]      
Balance at beginning of year $ 1,719 $ 1,069 $ 1,055
Additions 754 648 153
Write-offs (584) (101) (59)
Currency impact (50) 103 (80)
Balance at end of year $ 1,839 $ 1,719 $ 1,069