Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

v3.8.0.1
Income Taxes - Additional Information (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Income Taxes [Line Items]    
Increase in the valuation allowance $ 5,500,000  
Uncertain tax positions interest and penalties accrued 0 $ 0
Effect of remeasurement of deferred tax assets and liabilities under Tax Cuts and Jobs Act 3,700,000  
Federal    
Income Taxes [Line Items]    
Net operating loss carryforward 24,500,000  
State    
Income Taxes [Line Items]    
Net operating loss carryforward 21,300,000  
Germany | Corporate Income Tax Carryforwards    
Income Taxes [Line Items]    
Net operating loss carryforward 46,100,000  
Germany | Trade Tax Carryforwards    
Income Taxes [Line Items]    
Net operating loss carryforward $ 45,600,000  
Australia    
Income Taxes [Line Items]    
Australian tax credit from R&D activities   1,500,000
Income taxes receivable   $ 1,500,000