Quarterly report pursuant to Section 13 or 15(d)

Segment and Geographic Information - Additional Information (Details)

v3.8.0.1
Segment and Geographic Information - Additional Information (Details) - Segment
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]    
Number of Reportable Segments 1  
Customer Concentration Risk | Sales Revenue, Net    
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]    
Concentration risk, percentage 54.00% 46.00%
United Kingdom | Customer Concentration Risk | Sales Revenue, Net    
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]    
Concentration risk, percentage 46.00% 52.00%