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Stock-Based Compensation - Additional Information (Details)
1 Months Ended 12 Months Ended
Apr. 17, 2018
Installment
shares
Nov. 29, 2017
shares
Oct. 11, 2017
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
May 31, 2018
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Shares available for issuance       4,159,626   4,159,626 2,773,249  
Recognized stock-based compensation expense | $           $ 3,694,000 $ 2,793,000 $ 470,000
Options Issued and Outstanding                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Shares available for issuance       2,562,800   2,562,800 1,122,677  
Aggregate intrinsic value of options exercised | $           $ 67,000 $ 78,000  
Option granted           1,896,527    
Options Issued and Outstanding | Employees and Directors                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Option granted           1,886,687    
Weighted-average grant date fair value of options granted | $ / shares           $ 4.83    
Options Issued and Outstanding | Employees                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Option granted             926,838  
Weighted-average grant date fair value of options granted | $ / shares             $ 9.23  
Unrecognized compensation expense | $       $ 9,400,000   $ 9,400,000    
Unrecognized compensation expense, estimated weighted-average period for recognition           2 years 9 months 18 days    
Options Issued and Outstanding | Non-employees                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Option granted           9,840 7,200  
Weighted-average grant date fair value of options granted | $ / shares           $ 7.61 $ 12.51  
Unrecognized compensation expense | $       26,000   $ 26,000    
Unrecognized compensation expense, estimated weighted-average period for recognition           2 years 1 month 20 days    
Restricted Stock                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Shares granted 2,000              
Number of quarterly installment in which restriction lapse | Installment 4              
Recognized stock-based compensation expense | $           $ 4,000,000 $ 900,000 $ 400,000
Unrecognized stock-based compensation expense | $       $ 0   $ 0    
Restricted stock units                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Shares available for issuance       828,935   828,935 24,960  
Unrecognized compensation expense, estimated weighted-average period for recognition           3 years 9 months    
Shares granted           813,335    
Recognized stock-based compensation expense | $           $ 74,000 $ 35,000  
Unrecognized stock-based compensation expense | $       $ 1,100,000   $ 1,100,000    
Restricted stock units | Employees                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Shares granted       813,335 24,960      
Weighted-average grant date fair value | $ / shares       $ 1.27 $ 9.03      
2017 Stock Incentive Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of shares reserved for issuance   630,662 537,914 537,914   537,914    
Number of additional shares reserved for issuance   1,866,009 630,662          
2017 Stock Incentive Plan | Maximum                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Terms of stock based options granted           10 years    
2018 Stock Incentive Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Percentage of additional shares added on outstanding shares           4.00%    
Shares available for issuance       0   0    
2018 Stock Incentive Plan | Minimum [Member]                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of shares reserved for issuance       2,200,260   2,200,260    
2018 Stock Incentive Plan | Maximum                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of shares reserved for issuance       3,322,473   3,322,473    
2018 Employee Stock Purchase Plan                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of shares reserved for issuance             275,030  
Percentage of additional shares added on outstanding shares             1.00%  
Number of shares available for sale           0 0  
2018 Employee Stock Purchase Plan | Minimum [Member]                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of additional shares reserved for issuance             543,926  
2018 Employee Stock Purchase Plan | Maximum                
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                
Number of additional shares reserved for issuance             555,583