Annual report pursuant to Section 13 and 15(d)

Segment Information (Narrative) (Details)

v3.8.0.1
Segment Information (Narrative) (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
segment
Dec. 31, 2016
USD ($)
Dec. 31, 2015
Aug. 21, 2017
USD ($)
Number of segments | segment 2      
Preliminary assets $ 207,449 $ 210,457    
Sierra [Member]        
Preliminary assets $ 77,270     $ 80,566
Sales Revenue, Goods, Net [Member]        
Concentration risk, percentage     17.00%  
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member]        
Concentration risk, percentage 14.00% 16.00% 17.00%