SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND PRACTICES - Goodwill Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 0	$ 0		$ 0	$ 191,788
Goodwill [Roll Forward]
Goodwill, Gross, beginning balance				358,380
Accumulated Impairment, beginning balance				(267,029)
Goodwill, Net, beginning balance				91,351
Goodwill, Foreign Currency Translation Gain (Loss)				(747)
Goodwill, Gross, ending balance	357,633			357,633
Accumulated Impairment, ending balance	(267,029)			(267,029)
Goodwill, Net, ending balance	90,604			90,604
IHT
Goodwill [Line Items]
Goodwill, Impairment Loss			$ 191,800
Goodwill [Roll Forward]
Goodwill, Gross, beginning balance				212,928
Accumulated Impairment, beginning balance				(212,928)
Goodwill, Net, beginning balance				0
Goodwill, Foreign Currency Translation Gain (Loss)				0
Goodwill, Gross, ending balance	212,928			212,928
Accumulated Impairment, ending balance	(212,928)			(212,928)
Goodwill, Net, ending balance	0			0
MS
Goodwill [Roll Forward]
Goodwill, Gross, beginning balance				110,721
Accumulated Impairment, beginning balance				(54,101)
Goodwill, Net, beginning balance				56,620
Goodwill, Foreign Currency Translation Gain (Loss)				(420)
Goodwill, Gross, ending balance	110,301			110,301
Accumulated Impairment, ending balance	(54,101)			(54,101)
Goodwill, Net, ending balance	56,200			56,200
Quest Integrity
Goodwill [Roll Forward]
Goodwill, Gross, beginning balance				34,731
Accumulated Impairment, beginning balance				0
Goodwill, Net, beginning balance				34,731
Goodwill, Foreign Currency Translation Gain (Loss)				(327)
Goodwill, Gross, ending balance	34,404			34,404
Accumulated Impairment, ending balance	0			0
Goodwill, Net, ending balance	$ 34,404			$ 34,404