INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Net definite-lived intangible assets	$ 22,603	$ 23,995
B&W Vølund
Finite-Lived Intangible Assets [Line Items]
Net definite-lived intangible assets	500	1,100
B&W SPIG
Finite-Lived Intangible Assets [Line Items]
Net definite-lived intangible assets	$ 21,100	$ 21,600