REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 251,265	$ 238,873	$ 469,841	$ 433,491
Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	121,426	116,535	227,415	204,147
Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	106,846	97,356	198,640	183,413
Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	15,843	17,275	29,739	31,419
Other
Disaggregation of Revenue [Line Items]
Revenues	7,150	7,707	14,047	14,512
United States and Canada
Disaggregation of Revenue [Line Items]
Revenues	207,858	196,617	379,857	354,943
Other Countries
Disaggregation of Revenue [Line Items]
Revenues	43,407	42,256	89,984	78,548
IHT
Disaggregation of Revenue [Line Items]
Revenues	114,124	117,462	209,721	208,601
IHT | Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	91,701	92,291	168,152	163,820
IHT | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	115	207	139	288
IHT | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	15,787	17,267	29,626	30,722
IHT | Other
Disaggregation of Revenue [Line Items]
Revenues	6,521	7,697	11,804	13,771
IHT | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues	111,541	114,834	204,919	204,059
IHT | Other Countries
Disaggregation of Revenue [Line Items]
Revenues	2,583	2,628	4,802	4,542
MS
Disaggregation of Revenue [Line Items]
Revenues	107,416	97,167	200,857	184,563
MS | Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
MS | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	106,731	97,149	198,501	183,125
MS | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	56	8	113	697
MS | Other
Disaggregation of Revenue [Line Items]
Revenues	629	10	2,243	741
MS | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues	77,683	65,303	141,614	125,349
MS | Other Countries
Disaggregation of Revenue [Line Items]
Revenues	29,733	31,864	59,243	59,214
Quest Integrity
Disaggregation of Revenue [Line Items]
Revenues	29,725	24,244	59,263	40,327
Quest Integrity | Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	29,725	24,244	59,263	40,327
Quest Integrity | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Quest Integrity | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Quest Integrity | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Quest Integrity | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues	18,634	16,480	33,324	25,535
Quest Integrity | Other Countries
Disaggregation of Revenue [Line Items]
Revenues	$ 11,091	$ 7,764	$ 25,939	$ 14,792