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Stock-Based Compensation (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Stock-Based Compensation Expense Items [Abstract]    
Stock-based compensation expense $ 355 $ 380
Selling, General and Administrative Expense [Member]    
Stock-Based Compensation Expense Items [Abstract]    
Stock-based compensation expense 327 354
Research and Development Expense [Member]    
Stock-Based Compensation Expense Items [Abstract]    
Stock-based compensation expense $ 28 $ 26