REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing		Customers are generally billed as we satisfy our performance obligations and payment terms typically range from 30 to 90 days from the invoice date. Billings under certain fixed-price contracts may be based upon the achievement of specified milestones, while some arrangements may require advance customer payment. Our contracts do not include significant financing components since the contracts typically span less than one year.
Warranty term		12 months
Revenues	[1]	$ 874,553	$ 852,539	$ 1,163,314
United States and Canada
Disaggregation of Revenue [Line Items]
Revenues		709,324	693,846
Other Countries
Disaggregation of Revenue [Line Items]
Revenues		165,229	158,693
Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues		405,560	380,153
Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues		375,352	388,519
Heat Treating
Disaggregation of Revenue [Line Items]
Revenues		60,661	51,308
Other Services
Disaggregation of Revenue [Line Items]
Revenues		32,980	32,559
IHT
Disaggregation of Revenue [Line Items]
Revenues		415,371	374,740
IHT | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues		405,007	365,847
IHT | Other Countries
Disaggregation of Revenue [Line Items]
Revenues		10,364	8,893
IHT | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues		325,204	294,838
IHT | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues		467	206
IHT | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues		59,855	50,220
IHT | Other Services
Disaggregation of Revenue [Line Items]
Revenues		29,845	29,476
MS
Disaggregation of Revenue [Line Items]
Revenues		378,826	392,484
MS | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues		256,806	278,882
MS | Other Countries
Disaggregation of Revenue [Line Items]
Revenues		122,020	113,602
MS | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues		0	0
MS | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues		374,885	388,313
MS | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues		806	1,088
MS | Other Services
Disaggregation of Revenue [Line Items]
Revenues		3,135	3,083
Quest Integrity
Disaggregation of Revenue [Line Items]
Revenues		80,356	85,315
Quest Integrity | United States and Canada
Disaggregation of Revenue [Line Items]
Revenues		47,511	49,117
Quest Integrity | Other Countries
Disaggregation of Revenue [Line Items]
Revenues		32,845	36,198
Quest Integrity | Asset Integrity Management
Disaggregation of Revenue [Line Items]
Revenues		80,356	85,315
Quest Integrity | Repair and Maintenance Services
Disaggregation of Revenue [Line Items]
Revenues		0	0
Quest Integrity | Heat Treating
Disaggregation of Revenue [Line Items]
Revenues		0	0
Quest Integrity | Other Services
Disaggregation of Revenue [Line Items]
Revenues		$ 0	$ 0

[1] Revenues attributable to individual countries/geographic areas are based on the country of domicile of the legal entity that performs the work.