SEGMENT AND GEOGRAPHICAL INFORMATION - Segment Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Oct. 01, 2021
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	$ 395,111	$ 394,422	$ 386,906
Energy
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	336,036		331,573
Engineering and Consulting
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	22,630		23,134
Operating Segments [Member] | Energy
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	336,036		331,573
Operating Segments [Member] | Engineering and Consulting
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	22,630		23,134
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	59,575		55,329
Intersegment Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Segment assets	$ (23,130)		$ (23,130)