Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

v3.10.0.1
Income Taxes - Additional Information (Details) - USD ($)
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Income Tax Contingency [Line Items]        
Corporate tax rate   21.00% 34.00% 34.00%
Provisional net charge related to TCJA $ 7,578,000      
Tax expense (benefit) for change in valuation allowance     $ 767,000 $ 968,000
Unrecognized tax benefits, interest or penalties recognized   $ 0 0 0
Unrecognized tax benefits that, if recognized, would affect the effective tax rate 1,062,000 1,294,000 1,062,000 $ 934,000
California        
Income Tax Contingency [Line Items]        
Research and development credits carryforwards   2,800,000    
Valuation allowance $ 0 0 0  
Tax expense (benefit) for change in valuation allowance     $ 767,000  
Federal        
Income Tax Contingency [Line Items]        
Net operating loss carryforwards   $ 67,088,000    
Net operating loss carryforwards expiration, beginning year   2026    
Research and development credits carryforwards   $ 2,743,000    
Research and development credits carryforwards expiration, beginning year   2022    
State        
Income Tax Contingency [Line Items]        
Net operating loss carryforwards   $ 27,661,000    
Net operating loss carryforwards expiration, beginning year   2028