GOODWILL AND IMPAIRMENT CHARGES - Goodwill Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Goodwill [Roll Forward]
Balance at beginning of period	$ 282,006
Acquisitions	496
Foreign currency adjustments	(2,615)
Goodwill impairment loss	(191,788)	$ 0
Balance at end of period	88,099
IHT
Goodwill [Roll Forward]
Balance at beginning of period	193,216
Acquisitions	0
Foreign currency adjustments	(1,428)
Goodwill impairment loss	(191,788)
Balance at end of period	0
MS
Goodwill [Roll Forward]
Balance at beginning of period	55,409
Acquisitions	0
Foreign currency adjustments	(418)
Goodwill impairment loss	0
Balance at end of period	54,991
Quest Integrity
Goodwill [Roll Forward]
Balance at beginning of period	33,381
Acquisitions	496
Foreign currency adjustments	(769)
Goodwill impairment loss	0
Balance at end of period	$ 33,108