SEGMENT REPORTING - Financial Information of Company's Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	$ 220,193	$ 327,178	$ 772,577	$ 971,721
Income (loss) from operations	22,138	38,278	78,830	107,185
Impairment expense and other charges	48,401	0	48,401	0
Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	173,127	225,839	564,348	676,721
Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	4,057	4,284	12,368	12,149
Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,133	14,886	43,485	44,931
Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,876	82,169	152,376	237,920
SC
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	164,900	193,727	501,333	579,884
Income (loss) from operations	22,151	25,071	52,742	67,281
Impairment expense and other charges	22,200		22,200
SC | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	143,767	178,841	457,848	534,953
SC | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
SC | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,133	14,886	43,485	44,931
SC | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
IPS
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,876	82,169	152,376	237,920
Income (loss) from operations	(2,913)	10,097	16,080	28,924
Impairment expense and other charges	26,200		26,200
IPS | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
IPS | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
IPS | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
IPS | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	21,876	82,169	152,376	237,920
SCS
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	33,417	51,282	118,868	153,917
Income (loss) from operations	2,900	3,110	10,008	10,980
SCS | Product Sales | Recognized at a point in time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	29,360	46,998	106,500	141,768
SCS | Inventory Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	4,057	4,284	12,368	12,149
SCS | Staffing Services | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	0	0	0	0
SCS | Pump Production | Recognized over time
Segment Reporting Information, Profit (Loss) [Abstract]
Total Revenue	$ 0	$ 0	$ 0	$ 0