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Non - marketable Equity Investment - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2018
Jun. 30, 2018
Dec. 31, 2020
May 31, 2019
Jan. 31, 2019
Schedule Of Investments [Line Items]          
Reduction in carrying value on cumulative basis     $ 1.4    
Other Income and Expense, Net          
Schedule Of Investments [Line Items]          
Unrealized loss on equity investment     $ 1.4    
2018 Note and Warrant Purchase Agreement          
Schedule Of Investments [Line Items]          
Purchase of convertible note $ 0.4 $ 0.4      
Convertible note accrued interest rate 8.00% 8.00%      
Debt instrument maturity date 1 year 1 year      
2018 Note and Warrant Purchase Agreement | Common Stock          
Schedule Of Investments [Line Items]          
Warrants exercised to acquire shares       253,120  
2018 Note and Warrant Purchase Agreement | Series B Preferred Stock          
Schedule Of Investments [Line Items]          
Preferred stock value         $ 0.8