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Income Taxes, Valuation Allowance, Operating Loss Carryforwards and Tax Credit Carry-forwards (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Income Taxes [Abstract]    
Net change in valuation allowance $ 1,816  
Income Taxes [Abstract]    
Net operating loss carryforwards 19,573 $ 25,403
Federal [Member]    
Income Taxes [Abstract]    
Net operating loss carryforwards $ 131,055  
Operating loss carryforwards, expiration dates Dec. 31, 2028  
Federal [Member] | Research and Development [Member]    
Tax credit carryforwards [Abstract]    
Tax credit carryforwards $ 1,730  
Federal tax credit carryforward, expiration dates Dec. 31, 2032  
State [Member]    
Income Taxes [Abstract]    
Net operating loss carryforwards $ 107,989  
Operating loss carryforwards, expiration dates Dec. 31, 2029