Annual report pursuant to Section 13 and 15(d)

Income Taxes - Additional Information (Details)

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Income Taxes - Additional Information (Details) - USD ($)
1 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Taxes Disclosure [Line Items]        
Provision for income taxes   $ 0 $ 0 $ 0
Research and development tax credit utilized against employer's portion of payroll tax $ 250,000      
Research and development tax credit utilized as reduction of payroll expenses   373,000 284,000 175,000
Valuation allowance increased   9,200,000 $ 7,600,000 $ 5,100,000
Benefit for deferred tax assets   0    
Unrecognized tax benefits   868,000    
Liability related to uncertain tax positions   0    
Accrued interest and penalties related to gross unrecognized tax benefits   0    
Australian Taxation Office        
Income Taxes Disclosure [Line Items]        
Net operating loss (NOL) carryforwards   1,900,000    
Federal        
Income Taxes Disclosure [Line Items]        
Net operating loss (NOL) carryforwards   $ 109,700,000    
Net operating loss carryforwards expiration start year   2035    
Net operating loss (NOL) carryforwards indefinite   $ 87,600,000    
Federal | Research and Development        
Income Taxes Disclosure [Line Items]        
Tax credit carryforward expiration start year   2035    
Tax credit carryforward   $ 2,400,000    
State        
Income Taxes Disclosure [Line Items]        
Net operating loss (NOL) carryforwards   $ 17,300,000    
Net operating loss carryforwards expiration start year   2035    
State | Research and Development        
Income Taxes Disclosure [Line Items]        
Tax credit carryforward   $ 1,800,000