Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Details)

v3.8.0.1
Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Share-based compensation expense $ 3,597 $ 1,519 $ 1,592
Research and Development Expense [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Share-based compensation expense 1,016 554 528
General and Administrative Expense [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Share-based compensation expense $ 2,581 $ 965 $ 1,064