Annual report pursuant to Section 13 and 15(d)

Organization and Description of Business Operations (Details Textual)

v3.8.0.1
Organization and Description of Business Operations (Details Textual) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Mar. 08, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Retained Earnings (Accumulated Deficit)   $ (59,030) $ (36,353)  
Payments of Stock Issuance Costs   $ 0 $ 0 $ 6,321
Underwritten Public Offering [Member] | Subsequent Event [Member]        
Stock Issued During Period, Shares, New Issues 4,600,000      
Shares Issued, Price Per Share $ 4.35      
Stock Issued During Period, Value, New Issues $ 23,000      
Proceeds from Issuance Underwritten Public Offering 20,900      
Payments of Stock Issuance Costs $ 2,100      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period 690,000