Segment Reporting and Significant Customers (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
segment
Mar. 31, 2017
USD ($)
Segment Reporting and Significant Customers    
Number of reporting segment | segment 1  
Total revenue $ 10,042 $ 5,297
United States    
Segment Reporting and Significant Customers    
Total revenue 8,744 4,508
Europe    
Segment Reporting and Significant Customers    
Total revenue $ 1,298 $ 789