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Share-Based Compensation - Additional Information (Details) - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation expenses $ 501,000 $ 144,000
Weighted-average grant-date fair value of stock options granted $ 8.93  
Intrinsic value of stock options exercised $ 6,800,000  
Stock Options Outstanding    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation expenses 400,000 100,000
Unrecognized compensation cost related to non-vested stock options $ 6,800,000  
Non-vested awards not yet recognized weighted-average period for recognition 3 years 6 months  
Restricted Stock Awards and Restricted Stock Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Non-vested awards not yet recognized weighted-average period for recognition 3 years 1 month 6 days  
Unrecognized compensation cost related to non-vested restricted stock $ 2,800,000  
Fair value of restricted stock vested 100,000  
Maximum | Restricted Stock Awards and Restricted Stock Units    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Share-based compensation expenses $ 100,000 $ 100,000
2018 Equity Incentive Plan    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Annual percentage increase in number of shares authorized for issuance 4.00%  
Vesting terms of stock options Stock options vest 25% upon the first anniversary of the date of grant and the remainder ratably monthly thereafter for 36 months  
Shares available for future issuance 1,500,000  
2018 Equity Incentive Plan | First Anniversary of Date of Grant    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Vesting percentage of stock options 25.00%  
2018 Equity Incentive Plan | Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of shares authorized for issuance 1,400,000  
Maximum contractual term of stock options 10 years