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Note Payable - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Oct. 29, 2019
Sep. 30, 2020
Sep. 30, 2020
Dec. 31, 2019
Debt Instrument [Line Items]        
Interest expense   $ 730,000 $ 2,165,000  
Loan and Security Agreement [Member]        
Debt Instrument [Line Items]        
Interest expense   730,000 $ 2,165,000  
Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Credit facility, interest rate 9.65%      
Credit facility, payment terms     The Company will make interest only payments through December 1, 2021. The interest only period may be extended to June 1, 2022 upon satisfaction of certain milestones. Following the interest only period, the Company will repay the principal balance and interest of the advances in equal monthly installments through November 1, 2023.  
Percentage of prepayment amount during first year 3.00%      
Percentage of prepayment amount during second year 2.00%      
Percentage of prepayment amount during third year 1.00%      
Prepayment or repayment percentage 4.85%      
Additional advance prepayment or repayment percentage 4.85%      
Carrying value of debt   $ 24,977,000 $ 24,977,000 $ 24,648,000
Loan and Security Agreement [Member] | Term Loan Facility [Member] | Prime Rate [Member]        
Debt Instrument [Line Items]        
Debt instrument, variable rate 4.40%      
Hercules Capital, Inc. [Member] | Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Credit facility, aggregate principal amount $ 50,000,000      
First Tranche [Member] | Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Prepayment or repayment charge 1,213,000      
Carrying value of debt $ 24,575,000      
Debt instrument, interest rate effective percentage 11.47%      
First Tranche [Member] | Hercules Capital, Inc. [Member] | Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Gross proceeds from debt $ 25,000,000      
Second Tranche Unavailable to Borrow Due to Not Met Milestone Requirements [Member] | Hercules Capital, Inc. [Member] | Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Credit facility, aggregate principal amount 12,500,000      
Third Tranche Available Upon Approval on or Prior to June 30, 2021 [Member] | Hercules Capital, Inc. [Member] | Loan and Security Agreement [Member] | Term Loan Facility [Member]        
Debt Instrument [Line Items]        
Credit facility, aggregate principal amount $ 12,500,000