Quarterly report pursuant to Section 13 or 15(d)

REVENUES - Operating Revenue (Details)

v3.8.0.1
REVENUES - Operating Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Disaggregation of Revenue [Line Items]    
Operating revenues $ 54,750 $ 51,134
Revenues 57,322 54,527
United States    
Disaggregation of Revenue [Line Items]    
Operating revenues 39,133 33,967
Foreign    
Disaggregation of Revenue [Line Items]    
Operating revenues 15,617  
Oil and Gas    
Disaggregation of Revenue [Line Items]    
Operating revenues 52,153 47,454
Oil and Gas | United States    
Disaggregation of Revenue [Line Items]    
Operating revenues 36,536 30,287
Oil and Gas | Foreign    
Disaggregation of Revenue [Line Items]    
Operating revenues 15,617 17,167
Emergency response services    
Disaggregation of Revenue [Line Items]    
Operating revenues 2,597 3,680
Dry-leasing | United States    
Disaggregation of Revenue [Line Items]    
Revenues 571 234
Dry-leasing | Foreign    
Disaggregation of Revenue [Line Items]    
Revenues $ 2,001 $ 3,159