Quarterly report pursuant to Section 13 or 15(d)

Employee Stock Purchase Plan and Stock-Based Compensation - Summary of Option Activity (Details)

v3.10.0.1
Employee Stock Purchase Plan and Stock-Based Compensation - Summary of Option Activity (Details) - 2004 Plan and 2018 Equity Incentive Plan - USD ($)
$ / shares in Units, $ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Shares Available for Grant, Beginning Balance 91,149  
Shares Available for Grant, Increase in authorized shares 5,053,013  
Shares Available for Grant, Granted (2,570,848)  
Shares Available for Grant, Exercised 0  
Shares Available for Grant, Canceled 3,721  
Shares Available for Grant, Ending Balance 2,577,035 91,149
Outstanding Options, Beginning Balance 835,320  
Options granted to purchase common stock 2,570,848  
Outstanding Options Exercised (19,691)  
Outstanding Options Canceled (3,721)  
Outstanding Options, Ending Balance 3,382,756 835,320
Outstanding Options Exercisable 650,197  
Outstanding Options Vested and expected to vest 3,172,528  
Weighted - Average Exercise Price, Beginning Balance $ 10.31  
Weighted - Average Exercise Price, Granted 13.15  
Weighted - Average Exercise Price, Exercised 6.67  
Weighted - Average Exercise Price, Canceled 13.58  
Weighted - Average Exercise Price, Ending Balance 0 $ 10.31
Weighted - Average Exercise Price, Exercisable 0  
Weighted - Average Exercise Price, Vested and expected to vest $ 0  
Weighted - Average Remaining Contract Term 8 years 5 months 4 days 6 years 10 months 2 days
Weighted - Average Remaining Contract Term, Exercisable 5 years 9 months 18 days  
Weighted - Average Remaining Contract Term, Vested and expected to vest 8 years 4 months 20 days  
Aggregate Intrinsic Value, Balance $ 8,434 $ 3,813
Aggregate Intrinsic Value, Exercisable 3,486  
Aggregate Intrinsic Value, Vested and expected to vest $ 8,073