SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND PRACTICES - Schedule of Rollforward Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Goodwill [Line Items]
Accumulated impairment loss	$ 75,200	$ 75,200
Goodwill [Roll Forward]
Balance at beginning of period	281,650
Foreign currency adjustments	506
Balance at end of period	282,156
IHT
Goodwill [Line Items]
Accumulated impairment loss	21,100	21,100
Goodwill [Roll Forward]
Balance at beginning of period	192,608
Foreign currency adjustments	591
Balance at end of period	193,199
MS
Goodwill [Line Items]
Accumulated impairment loss	54,100	$ 54,100
Goodwill [Roll Forward]
Balance at beginning of period	55,627
Foreign currency adjustments	(87)
Balance at end of period	55,540
Quest Integrity
Goodwill [Roll Forward]
Balance at beginning of period	33,415
Foreign currency adjustments	2
Balance at end of period	$ 33,417