RESTRUCTURING ACTIVITIES - Summary of Restructuring Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring activities	$ 1,021	$ (102)	$ 1,405	$ (8)
Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring activities	152	(187)	67	(356)
Other
Restructuring Cost and Reserve [Line Items]
Restructuring activities	869	85	1,338	348
Operating Segments | B&W Renewable segment
Restructuring Cost and Reserve [Line Items]
Restructuring activities	477	(20)	388	(213)
Operating Segments | B&W Renewable segment | Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring activities	152	(34)	63	(263)
Operating Segments | B&W Renewable segment | Other
Restructuring Cost and Reserve [Line Items]
Restructuring activities	325	14	325	50
Operating Segments | B&W Environmental segment
Restructuring Cost and Reserve [Line Items]
Restructuring activities	164	34	184	103
Operating Segments | B&W Environmental segment | Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring activities	0	9	1	19
Operating Segments | B&W Environmental segment | Other
Restructuring Cost and Reserve [Line Items]
Restructuring activities	164	25	183	84
Operating Segments | B&W Thermal segment
Restructuring Cost and Reserve [Line Items]
Restructuring activities	830	82	833	280
Operating Segments | B&W Thermal segment | Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring activities	0	66	3	116
Operating Segments | B&W Thermal segment | Other
Restructuring Cost and Reserve [Line Items]
Restructuring activities	830	16	830	164
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring activities	(450)	(198)	0	(178)
Corporate | Severance and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring activities	0	(228)	0	(228)
Corporate | Other
Restructuring Cost and Reserve [Line Items]
Restructuring activities	$ (450)	$ 30	$ 0	$ 50