SEGMENT REPORTING - Financial Information of Company's Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	$ 245,616	$ 300,983
Income (loss) from operations	25,386	31,109
Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	197,148	213,947
Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	4,196	4,225
Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,027	12,790
Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	23,245	70,021
SC
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	186,398	182,585
Income (loss) from operations	22,116	16,926
SC | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	165,371	169,795
SC | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
SC | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,027	12,790
SC | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
IPS
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	23,245	70,021
Income (loss) from operations	947	10,428
IPS | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
IPS | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
IPS | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
IPS | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	23,245	70,021
SCS
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	35,973	48,377
Income (loss) from operations	2,323	3,755
SCS | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	31,777	44,152
SCS | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	4,196	4,225
SCS | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0
SCS | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	$ 0	$ 0