Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Summary of Sales by Major Customer (Details)

v3.7.0.1
Summary of Significant Accounting Policies - Summary of Sales by Major Customer (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Concentration Risk [Line Items]        
Amount $ 34,240 $ 27,271 $ 62,250 $ 55,741
Net Sales | Customer Concentration Risk        
Concentration Risk [Line Items]        
Percent of Total 100.00% 100.00% 100.00% 100.00%
Caterpillar        
Concentration Risk [Line Items]        
Amount $ 7,015 $ 4,792 $ 11,554 $ 12,019
Caterpillar | Net Sales | Customer Concentration Risk        
Concentration Risk [Line Items]        
Percent of Total 20.00% 18.00% 19.00% 21.00%
CEG Distributions PTY Ltd.        
Concentration Risk [Line Items]        
Amount $ 3,973 $ 2,668 $ 6,887 $ 5,407
CEG Distributions PTY Ltd. | Net Sales | Customer Concentration Risk        
Concentration Risk [Line Items]        
Percent of Total 12.00% 10.00% 11.00% 10.00%
Other        
Concentration Risk [Line Items]        
Amount $ 23,252 $ 19,811 $ 43,809 $ 38,315
Other | Net Sales | Customer Concentration Risk        
Concentration Risk [Line Items]        
Percent of Total 68.00% 72.00% 70.00% 69.00%