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Inventories - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Inventory [Line Items]          
Write-off of inventory $ 0 $ 0 $ 496,000 $ 0  
Pre-launch Inventory          
Inventory [Line Items]          
Raw materials inventory $ 800,000   $ 800,000   $ 800,000