REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues	$ 228,618	$ 239,492	$ 428,218	$ 441,769
Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	90,113	94,305	171,123	175,911
Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	112,875	122,241	211,883	222,082
Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	17,707	15,928	31,298	29,934
Other
Disaggregation of Revenue [Line Items]
Revenues	7,923	7,018	13,914	13,842
IHT
Disaggregation of Revenue [Line Items]
Revenues	113,234	116,740	212,682	218,569
IHT | Non-Destructive Evaluation and Testing Services
Disaggregation of Revenue [Line Items]
Revenues	90,113	94,305	171,123	175,911
IHT | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues	2	219	147	222
IHT | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	17,459	15,717	30,943	29,445
IHT | Other
Disaggregation of Revenue [Line Items]
Revenues	5,660	6,499	10,469	12,991
MS
Disaggregation of Revenue [Line Items]
Revenues	115,384	122,752	215,536	223,200
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	112,873	122,022	211,736	221,860
MS | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues	248	211	355	489
MS | Other
Disaggregation of Revenue [Line Items]
Revenues	2,263	519	3,445	851
United States and Canada
Disaggregation of Revenue [Line Items]
Revenues	189,338	195,639	354,604	366,201
United States and Canada | IHT
Disaggregation of Revenue [Line Items]
Revenues	110,211	113,013	206,507	211,544
United States and Canada | MS
Disaggregation of Revenue [Line Items]
Revenues	79,127	82,626	148,097	154,657
Other Countries
Disaggregation of Revenue [Line Items]
Revenues	39,280	43,853	73,614	75,568
Other Countries | IHT
Disaggregation of Revenue [Line Items]
Revenues	3,023	3,727	6,175	7,025
Other Countries | MS
Disaggregation of Revenue [Line Items]
Revenues	$ 36,257	$ 40,126	$ 67,439	$ 68,543