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Stock-Based Compensation Plan - Narrative (Details) - USD ($)
3 Months Ended 6 Months Ended
Dec. 19, 2019
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Stock Based Compensation Plans [Line Items]          
Unamortized stock-based compensation expense for outstanding options   $ 1,800,000   $ 1,800,000  
Stock-based compensation expense   200,000 $ 100,000 300,000 $ 300,000
Aggregate intrinsic value of outstanding stock options   300,000   $ 300,000  
Weighted average vesting period       3 years 1 month 6 days  
Stock Incentive Plan 2017 [Member]          
Stock Based Compensation Plans [Line Items]          
Increase in number of shares reserved for grant 600,000        
Number of shares reserved for grant and issuance 660,000        
Expiration period (in years)       10 years  
Research and Development Expense [Member]          
Stock Based Compensation Plans [Line Items]          
Stock-based compensation expense   45,000 24,000 $ 100,000 45,000
General and Administrative Expense [Member]          
Stock Based Compensation Plans [Line Items]          
Stock-based compensation expense   $ 100,000 $ 100,000 $ 300,000 $ 200,000