BUSINESS SEGMENT INFORMATION - Operating segment revenues by major service lines (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue, Net	$ 436,334	$ 298,119
Operating Segments
Segment Reporting Information [Line Items]
Revenue, Net	436,334	298,119
Operating Segments | Technical Services
Segment Reporting Information [Line Items]
Revenue, Net	419,063	286,198
Operating Segments | Technical Services | Pressure Pumping
Segment Reporting Information [Line Items]
Revenue, Net	256,155	182,933
Operating Segments | Technical Services | Downhole Tools
Segment Reporting Information [Line Items]
Revenue, Net	93,041	52,345
Operating Segments | Technical Services | Coiled Tubing
Segment Reporting Information [Line Items]
Revenue, Net	25,196	21,379
Operating Segments | Technical Services | Nitrogen
Segment Reporting Information [Line Items]
Revenue, Net	11,431	8,676
Operating Segments | Technical Services | Snubbing
Segment Reporting Information [Line Items]
Revenue, Net	3,973	5,643
Operating Segments | Technical Services | All Other Technical Services
Segment Reporting Information [Line Items]
Revenue, Net	29,267	15,222
Operating Segments | Support Services
Segment Reporting Information [Line Items]
Revenue, Net	17,271	11,921
Operating Segments | Support Services | Rental Tools
Segment Reporting Information [Line Items]
Revenue, Net	10,020	5,389
Operating Segments | Support Services | All Other Support Services
Segment Reporting Information [Line Items]
Revenue, Net	$ 7,251	$ 6,532