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Equity Incentive Plans and Stock-Based Compensation - 2014 Equity Incentive Plan/ESPP (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Sep. 30, 2018
Jun. 10, 2015
Oct. 31, 2018
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Intrinsic value of options exercised       $ 2,778 $ 1,930 $ 2,629
2014 Stock Incentive Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of shares available for future grant (in shares)       10,725,127    
Expiration period       5 years    
2014 Stock Incentive Plan | Stock options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Expiration period       10 years    
Vesting period       4 years    
2014 Stock Incentive Plan | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of exercise price of fair value per share on grant date       110.00%    
2014 Stock Incentive Plan | Minimum | Non-Statutory Stock Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of exercise price of fair value per share on grant date       100.00%    
2014 Stock Incentive Plan | Minimum | Restricted Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       1 year    
2014 Stock Incentive Plan | Minimum | Performance Stock Units            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       1 year    
2014 Stock Incentive Plan | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Additional shares reserved for future issuance (in shares)   8,000,000        
Percentage of outstanding shares of common stock   5.00%        
Combined voting power of all classes of stock       10.00%    
2014 Stock Incentive Plan | Maximum | Restricted Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       4 years    
2014 Stock Incentive Plan | Maximum | Performance Stock Units            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period       4 years    
2014 Employee Stock Purchase Plan | ESPP            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of eligible compensation 15.00%          
Offering period 24 months          
Amended 2014 Employee Stock Purchase Plan | ESPP            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of shares available for future grant (in shares)       1,821,186    
Percentage of eligible compensation     10.00%      
Offering period     6 months      
Percentage of market value       85.00%    
Maximum number of shares per employee (in shares)       1,500    
ESPP            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares purchased (in shares)       581,634 662,362  
Price per share (in dollars per share)       $ 5.67 $ 5.14  
Intrinsic value of options exercised       $ 1,000 $ 800