Quarterly report pursuant to Section 13 or 15(d)

Loan and Security Agreement - Additional Information (Details)

v3.19.2
Loan and Security Agreement - Additional Information (Details)
1 Months Ended 3 Months Ended 6 Months Ended
Aug. 31, 2017
USD ($)
Installment
Jun. 30, 2019
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2019
USD ($)
Jun. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Oct. 01, 2018
shares
Jul. 31, 2018
USD ($)
Debt Instrument [Line Items]                
Debt, non-current   $ 7,000,000   $ 7,000,000   $ 10,000,000    
Interest expense, debt   300,000 $ 300,000 600,000 $ 600,000      
Two Thousand Seventeen Warrants                
Debt Instrument [Line Items]                
Estimated fair value portion of preferred stock               $ 300,000
Two Thousand Seventeen Warrants | Series E Redeemable Convertible Preferred Stock                
Debt Instrument [Line Items]                
Warrant to purchase stock | shares             46,359  
August 2017 Loan                
Debt Instrument [Line Items]                
Debt, current   5,800,000   5,800,000        
Debt, non-current   7,000,000   7,000,000        
Interest payable $ 600,000 400,000   $ 400,000        
Average interest rate       8.88%        
Final payment fee percentage 3.83%              
Loan and accretion of debt discount   $ 85,000 $ 86,000 $ 175,000 $ 168,000      
August 2017 Loan | Floating Rate                
Debt Instrument [Line Items]                
Interest charges on loan 7.39%              
August 2017 Loan | LIBOR                
Debt Instrument [Line Items]                
Interest charges on loan 6.40%              
Description of interest charges on loan       the sum of the 30-day U.S. Dollar London Interbank Offered Rate (“LIBOR”) plus 6.40%.        
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | August 2017 Loan                
Debt Instrument [Line Items]                
Borrowed amount $ 15,000,000              
Loan and Security Agreement | Oxford Finance LLC and Silicon Valley Bank | August 2017 Loan | March 2019                
Debt Instrument [Line Items]                
Number of monthly installments | Installment 30              
Payment terms, description       The loan is due in 30 monthly installments from March 2019 through its repayment in August 2021, with interest-only monthly payments until March 2019.        
Repayment installment, start date, month and year 2019-03              
Repayment installment, end date, month and year 2021-08              
Frequency of interest-only payments       monthly payments        
Interest-only payments, maturity month and year 2019-03