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Summary of Significant Accounting Policies, Recent Accounting Pronouncements (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Recent Accounting Pronouncements [Abstract]    
Accumulated deficit $ (139,129) $ (141,370)
ASC 606 [Member]    
Recent Accounting Pronouncements [Abstract]    
Accumulated deficit   $ 3,900
ASU 2016-02 [Member] | Plan [Member]    
Recent Accounting Pronouncements [Abstract]    
Right-of-use asset 2,200  
Lease liability $ 2,200