SEGMENT AND GEOGRAPHIC DISCLOSURES - Segment Data for our Three Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 189,304	$ 315,829	$ 426,143	[1]	$ 585,428	[1]
Operating income (loss)	(4,366)	13,004	(217,298)		(3,524)
Capital expenditures	4,808	8,892	11,512	[2]	15,502	[2]
Depreciation and amortization	11,478	12,379	23,186		24,650
IHT
Segment Reporting Information [Line Items]
Revenues	80,474	138,658	188,355		265,714
MS
Segment Reporting Information [Line Items]
Revenues	92,820	144,897	197,339		266,423
Quest Integrity
Segment Reporting Information [Line Items]
Revenues	16,010	32,274	40,449		53,291
Operating segments | IHT
Segment Reporting Information [Line Items]
Revenues	80,474	138,658	188,355		265,714
Operating income (loss)	4,740	9,497	(187,410)	[3]	11,218
Capital expenditures	843	2,083	1,884	[2]	3,051	[2]
Depreciation and amortization	3,746	4,401	7,729		8,903
Operating segments | MS
Segment Reporting Information [Line Items]
Revenues	92,820	144,897	197,339		266,423
Operating income (loss)	9,899	20,317	10,921		25,851
Capital expenditures	2,446	2,624	6,063	[2]	4,587	[2]
Depreciation and amortization	5,475	5,518	10,906		10,932
Operating segments | Quest Integrity
Segment Reporting Information [Line Items]
Revenues	16,010	32,274	40,449		53,291
Operating income (loss)	689	9,324	6,795		10,968
Capital expenditures	1,044	1,249	2,015	[2]	2,577	[2]
Depreciation and amortization	887	999	1,773		1,920
Corporate and shared support services
Segment Reporting Information [Line Items]
Operating income (loss)	(19,694)	(26,134)	(47,604)		(51,561)
Capital expenditures	475	2,936	1,550	[2]	5,287	[2]
Depreciation and amortization	$ 1,370	$ 1,461	$ 2,778		$ 2,895

[1] Revenues attributable to individual countries/geographic areas are based on the country of domicile of the legal entity that performs the work.

[2] Totals may vary from amounts presented in the condensed consolidated statements of cash flows due to the timing of cash payments.

[3] Includes goodwill impairment charge for IHT as discussed in Note 7 that impacted operating income (loss) for the three months ended March 31, 2020 and six months ended June 30, 2020.