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Income Taxes - Summary of Movements in Valuation Allowance (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]    
Balance at beginning of year $ 8,601 $ 5,836
Change due to expense and foreign exchange (113) 395
Deductions 5,945 2,370
Balance at end of year $ 14,433 $ 8,601