SEGMENT AND GEOGRAPHIC DISCLOSURES - Segment Data for our Three Operating 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 [Line Items]
Revenues	$ 219,093	$ 290,079	$ 645,236	[1]	$ 875,507	[1]
Operating income (loss)	2,297	(1,840)	(215,001)		(5,364)
Capital expenditures	2,264	9,266	13,776	[2]	24,768	[2]
Depreciation and amortization	11,523	12,050	34,709		36,700
IHT
Segment Reporting Information [Line Items]
Revenues	96,637	126,379	284,992		392,093
MS
Segment Reporting Information [Line Items]
Revenues	101,738	135,625	299,077		402,048
Quest Integrity
Segment Reporting Information [Line Items]
Revenues	20,718	28,075	61,167		81,366
Operating segments | IHT
Segment Reporting Information [Line Items]
Revenues	96,637	126,379	284,992		392,093
Operating income (loss)	7,720	6,640	(179,690)	[3]	17,858
Capital expenditures	290	2,588	2,174	[2]	5,639	[2]
Depreciation and amortization	3,609	4,390	11,338		13,293
Operating segments | MS
Segment Reporting Information [Line Items]
Revenues	101,738	135,625	299,077		402,048
Operating income (loss)	9,581	15,871	20,502		41,722
Capital expenditures	657	3,795	6,720	[2]	8,382	[2]
Depreciation and amortization	5,491	5,411	16,397		16,343
Operating segments | Quest Integrity
Segment Reporting Information [Line Items]
Revenues	20,718	28,075	61,167		81,366
Operating income (loss)	3,006	7,122	9,801		18,090
Capital expenditures	1,079	1,038	3,094	[2]	3,615	[2]
Depreciation and amortization	969	814	2,742		2,734
Corporate and shared support services
Segment Reporting Information [Line Items]
Operating income (loss)	(18,010)	(31,473)	(65,614)		(83,034)
Capital expenditures	238	1,845	1,788	[2]	7,132	[2]
Depreciation and amortization	$ 1,454	$ 1,435	$ 4,232		$ 4,330

[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 nine months ended September 30, 2020.