Annual report pursuant to Section 13 and 15(d)

Debt - Additional Information (Details)

v3.19.1
Debt - Additional Information (Details) - USD ($)
 12 Months Ended
Apr. 27, 2018
Dec. 31, 2018
Dec. 20, 2018
Debt Instrument [Line Items]      
Maximum amount available under second draw   $ 15,000,000  
Amortization of debt discount and deferred financing costs   $ 360,000  
Ordinary Shares      
Debt Instrument [Line Items]      
Number of warrants to purchase shares 19,890    
Loan and Security Agreement | Silicon Valley Bank (SVB)      
Debt Instrument [Line Items]      
Loan and security agreement entered date   Apr. 27, 2018  
Initial draw amount under agreement $ 15,000,000    
Remaining borrowing facility available date Oct. 31, 2019    
Frequency of amortization payments   Monthly  
Date of first required payment of initial draw Nov. 01, 2019    
Extended date of first required payment if second draw funded Apr. 01, 2020    
Minimum fixed interest rate per annum 8.31%    
Final interest rate payment on outstanding principal 4.20%    
Principal and interest payment, maturity date Mar. 01, 2022    
Final payment fee $ 600,000    
Voluntary prepayment fee in first year 3.00%    
Voluntary prepayment fee in second year 2.00%    
Voluntary prepayment fee thereafter 1.00%    
Effective annual interest rate on outstanding debt     12.03%
Interest expense   $ 1,169,000  
Amortization of debt discount and deferred financing costs   $ 360,000  
Loan and Security Agreement | Silicon Valley Bank (SVB) | Wall Street Journal Prime Rate      
Debt Instrument [Line Items]      
Basis spread on interest rate 3.89%    
Loan and Security Agreement | Silicon Valley Bank (SVB) | Maximum      
Debt Instrument [Line Items]      
Maximum amount available under second draw $ 15,000,000    
Silicon Valley Bank and Life Sciences Fund II LLC      
Debt Instrument [Line Items]      
Percentage of purchase additional ordinary shares equal to term loan divided by applicable exercise price 2.50%    
Silicon Valley Bank and Life Sciences Fund II LLC | Series B Convertible Preferred Shares      
Debt Instrument [Line Items]      
Number of warrants to purchase shares 19,890    
Warrants to purchase convertible preferred shares, exercise price $ 18.85