Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

v3.8.0.1
Income Taxes - Additional Information (Details) - USD ($)
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Jan. 01, 2017
Operating Loss Carryforwards [Line Items]              
Income tax expense $ (44,000) $ 1,706,000   $ 1,662,000 $ 0 $ 0  
Federal statutory income tax rate       34.00% 34.00% 34.00%  
(Decrease) increase in the valuation allowance       $ (166,100,000) $ 8,200,000 $ 19,600,000  
Tax cuts and jobs act of 2017 change in tax rate income tax expense benefit       72,700,000      
Net operating loss carryforwards 4,701,000     4,701,000 123,672,000    
Exclude net operating tax credit carryforwards 12,225,000     12,225,000 25,297,000    
Unrecognized tax benefits that would impact effective tax rate 4,500,000     4,500,000      
Accrued interest or penalties related to uncertain tax positions 0     0      
Federal Orphan Credit [Member]              
Operating Loss Carryforwards [Line Items]              
Tax credit carry forward amount 1,000,000     $ 1,000,000      
Tax credit carryforward expiration year       2037      
State [Member]              
Operating Loss Carryforwards [Line Items]              
Net operating loss carry-forwards 27,300,000     $ 27,300,000      
Net operating loss carryforwards expiration year       2028      
California [Member]              
Operating Loss Carryforwards [Line Items]              
Net operating loss carry-forward expired       $ 24,300,000 $ 41,200,000 $ 22,400,000  
California [Member] | Research and Development [Member]              
Operating Loss Carryforwards [Line Items]              
Tax credit carry forward amount 19,800,000     19,800,000      
Federal [Member]              
Operating Loss Carryforwards [Line Items]              
Net operating loss carryforwards 119,800,000     119,800,000      
Exclude net operating tax credit carryforwards 15,400,000     15,400,000      
Net operating loss carry-forwards $ 13,600,000     $ 13,600,000      
Net operating loss carryforwards expiration year       2036      
ASU 2016-09 [Member]              
Operating Loss Carryforwards [Line Items]              
Net operating loss carryforwards             $ 1,800,000
Operating loss carryforwards, valuation allowance             $ 1,800,000
Scenario, Plan [Member]              
Operating Loss Carryforwards [Line Items]              
Federal statutory income tax rate     21.00%        
Tax cuts and jobs act of 2017 change in tax rate income tax expense benefit     $ 51,800,000