SEGMENT AND GEOGRAPHIC DISCLOSURES - Segment Data for our Three Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 194,618	$ 236,839
Operating income (loss)	(24,300)	(212,932)
Capital expenditures	4,397	6,704
Depreciation and amortization	10,959	11,708
IHT
Segment Reporting Information [Line Items]
Revenues	91,139	107,881
MS
Segment Reporting Information [Line Items]
Revenues	87,396	104,519
Quest Integrity
Segment Reporting Information [Line Items]
Revenues	16,083	24,439
Operating segments | IHT
Segment Reporting Information [Line Items]
Revenues	91,139	107,881
Operating income (loss)	364	(192,150)
Capital expenditures	2,714	1,041
Depreciation and amortization	3,470	3,983
Operating segments | MS
Segment Reporting Information [Line Items]
Revenues	87,396	104,519
Operating income (loss)	115	1,022
Capital expenditures	1,152	3,617
Depreciation and amortization	5,439	5,431
Operating segments | Quest Integrity
Segment Reporting Information [Line Items]
Revenues	16,083	24,439
Operating income (loss)	(252)	6,106
Capital expenditures	406	971
Depreciation and amortization	712	886
Corporate and shared support services
Segment Reporting Information [Line Items]
Operating income (loss)	(24,527)	(27,910)
Capital expenditures	125	1,075
Depreciation and amortization	$ 1,338	$ 1,408