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Stockholders' Equity - Stock-based Compensation Expenses (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Stock-based compensation $ 520 $ 745 $ 1,257 $ 1,463
General and Administrative Expense [Member]        
Stock-based compensation 348 494 825 1,039
Research and Development Expense [Member]        
Stock-based compensation $ 172 $ 251 $ 432 $ 424