Property and Equipment (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Property and equipment    
Property and equipment, gross $ 6,231 $ 7,602
Less accumulated depreciation and amortization 3,336 3,892
Property and equipment, net 2,895 3,710
Depreciation    
Depreciation expense 900 900
Machinery and Equipment [Member]    
Property and equipment    
Property and equipment, gross 2,029 2,598
Furniture and Fixtures [Member]    
Property and equipment    
Property and equipment, gross 963 1,031
Software [Member]    
Property and equipment    
Property and equipment, gross 41 666
Leasehold Improvements [Member]    
Property and equipment    
Property and equipment, gross $ 3,198 $ 3,307