Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Additional Information (Details)

v3.20.1
Stock-Based Compensation - Additional Information (Details)
12 Months Ended
Jun. 25, 2018
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
ExecutiveOfficer
$ / shares
shares
Dec. 31, 2017
USD ($)
Jun. 30, 2018
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of options granted   1,248,871      
Maximum number of shares issued upon exercise of incentive stock options   1,478,773      
Common stock, shares issued   19,208,077 19,114,421    
Weighted average grant date fair value of options granted | $ / shares   $ 13.36      
Aggregate intrinsic value of exercised stock options | $   $ 292,000      
Period for right to purchase underlying option shares lapses after applicable vesting commencement date   1 year      
Stock-based compensation expense recognized | $   $ 4,007,000 $ 1,993,000 $ 203,000  
Payments of dividends of common stock | $   $ 0      
Expected dividend yield   0.00%      
Early Exercise Stock Options          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Vesting period     36 months    
Nonvested common shares outstanding   30,027 68,349    
Percentage of underlying option shares whose right to purchase lapses after applicable vesting commencement date     25.00%    
Right to repurchase shares underlying shares     0.0208    
Other Current Liabilities | Early Exercise Stock Options          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares issued upon early exercise of stock options are subject to repurchase | $   $ 62,000 $ 112,000    
Employee options          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Unrecognized stock-based compensation cost | $   $ 10,300,000      
Estimated weighted average amortization period   2 years 6 months      
Expected term       6 years 1 month 6 days  
Employee options | Maximum          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Expected term   5 years 10 months 24 days 6 years 1 month 6 days    
Employee options | Minimum          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Expected term   5 years 9 months 18 days 5 years 6 months    
Stock Options Granted to Employees that Contain Performance Condition          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of options granted   0 115,657    
Stock-based compensation expense recognized | $     $ 474,000    
Number of executive officers granted with purchase option | ExecutiveOfficer     2    
Number of option vested 115,657        
Options vesting date     Jun. 25, 2018    
Stock-based compensation expense recognition period     2018-06    
Restricted Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Vesting period   4 years      
Nonvested common shares outstanding     20,908    
ESPP          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Expected term   6 months 6 months    
2018 Equity Incentive Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares available for future issuance   1,765,266      
Number of shares will increase automatically through every year on specified date   --01-01      
Number of shares increase automatically continuing through maximum period   beginning on January 1, 2019 and continuing through and including January 1, 2028      
2018 Equity Incentive Plan | Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Maximum number of shares authorized available for issuance   1,600,692      
Increase in number of shares reserved for issuance as percentage of total number of shares of capital stock outstanding on last date of preceding calendar year   5.00%      
2018 Equity Incentive Plan | Maximum | Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Maximum number of shares authorized available for issuance   4,000,000      
2018 Equity Incentive Plan | Employee options          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of options granted   1,271,992      
2018 Equity Incentive Plan | Incentive Stock Options | Maximum | Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Maximum number of shares issued upon exercise of incentive stock options   12,500,000      
2018 Equity Incentive Plan | Restricted Stock Units          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Number of RSU granted   0 10,189    
Weighted-average estimated grant-date fair value | $ / shares     $ 17.75    
Stock-based compensation expense recognized | $     $ 181,000    
2015 Equity Incentive Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Vesting period   4 years      
Options to purchase of common stock outstanding   1,835,074      
Weighted average grant date fair value of options granted | $ / shares   $ 9.33 $ 4.23    
Aggregate intrinsic value of exercised stock options | $   $ 292,000 $ 370,000    
2015 Equity Incentive Plan | Maximum          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Options granted expiry period   10 years      
2018 Employee Stock Purchase Plan | Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares available for future issuance   364,488     200,000
Common stock, shares issued   26,656      
Authorized an offering beginning period   Nov. 16, 2018      
Authorized an offering ending period   May 15, 2019      
Authorized an new offering beginning period   May 16, 2019      
Authorized an new offering ending period   Nov. 16, 2019      
2018 Employee Stock Purchase Plan | Maximum | Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Percentage of annual increase in number of common stock shares   1.00%      
Annual increase in number of common stock shares   375,000      
Option price per share of common stock at fair market value   85.00%