Annual report pursuant to Section 13 and 15(d)

Income Taxes Narrative (Details)

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Income Taxes Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Valuation Allowance [Line Items]      
Operating loss carryforwards $ 1,800,000    
Loss carryforward of foreign subsidiary and joint venture 283,000 $ 430,000  
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) 12,000 172,000 $ 0
Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense   11,900,000  
Federal and state research and development credit carryforwards 3,200,000    
Unrecognized tax benefit that would affect the effective tax rate 563,000    
Interest and penalties related to unrecognized tax benefits accrued 5,600 1,400  
Interest and penalties recognized related to unrecognized tax expense (benefits) $ (4,200) $ (1,000)  
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent 21.00% 34.00% 34.00%
Domestic Tax Authority      
Valuation Allowance [Line Items]      
Operating loss carryforwards $ 85,600,000    
State and Local Jurisdiction      
Valuation Allowance [Line Items]      
Operating loss carryforwards $ 63,300,000