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Stockholders' Equity - Equity Plan (Details)
12 Months Ended
Dec. 31, 2019
USD ($)
offering_period
shares
Jun. 30, 2018
shares
May 31, 2017
shares
Jan. 01, 2013
shares
2018 Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized for issuance   1,500,000    
Number of shares available for future grant 700,966      
2018 Plan | Stock Options | Share-based award tranche one        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period (in years) 2 years      
2018 Plan | Stock Options | Share-based award tranche two        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period (in years) 3 years      
2018 Plan | Stock Options | Share-based award tranche three        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Expiration period (in years) 10 years      
ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of offering periods | offering_period 2      
Term of offering period 6 months      
Maximum annual contribution per employee as percent of annual salary 15.00%      
Maximum annual contribution per employee | $ $ 25,000      
Purchase price measurement as percent of closing price on enrollment date 85.00%      
Purchase price measurement as percent of closing price on exercise date 85.00%      
2012 ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized for issuance       50,000
2017 ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized for issuance     100,000  
Amended 2017 ESPP        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of shares authorized for issuance   500,000    
Number of shares available for future grant 379,846      
Shares issued under ESPP 25,809