Annual report pursuant to Section 13 and 15(d)

Income Taxes (Details Textual)

v3.8.0.1
Income Taxes (Details Textual) - USD ($)
$ in Thousands
 1 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Line Items]          
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount     $ 24,400 $ 4,400 $ 2,700
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent     35.00%    
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount $ 32,600   $ 32,609 $ 0 $ 0
Scenario, Plan [Member]          
Income Tax Disclosure [Line Items]          
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent   21.00%      
California Franchise Tax Board [Member]          
Income Tax Disclosure [Line Items]          
Operating Loss Carry Forwards Expiration Year     2033    
Operating Loss Carryforwards 107,100   $ 107,100    
Domestic Tax Authority [Member]          
Income Tax Disclosure [Line Items]          
Operating Loss Carry Forwards Expiration Year     2037    
Operating Loss Carryforwards 261,000   $ 261,000    
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]          
Income Tax Disclosure [Line Items]          
Operating Loss Carry Forwards Expiration Year     2037    
Tax Credit Carryforward, Amount 8,900   $ 8,900    
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]          
Income Tax Disclosure [Line Items]          
Tax Credit Carryforward, Amount $ 8,800   $ 8,800