RESTRUCTURING ACTIVITIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Total	$ 2,396	$ 2,556	$ 6,739	$ 9,571
Severance and related costs	881	2,556	2,594	9,571
COVID-19 related costs	169		1,111
Other	1,346		3,034
B&W Renewable segment
Restructuring Cost and Reserve [Line Items]
Total	594		2,346
Severance and related costs	340	414	1,153	1,888
COVID-19 related costs	23		657
Other	231		536
B&W Environmental segment
Restructuring Cost and Reserve [Line Items]
Total	299		676
Severance and related costs	119	193	330	2,029
COVID-19 related costs	52		78
Other	128		268
B&W Thermal segment
Restructuring Cost and Reserve [Line Items]
Total	1,370		3,259
Severance and related costs	422	805	1,111	2,986
COVID-19 related costs	92		282
Other	856		1,866
Corporate
Restructuring Cost and Reserve [Line Items]
Total	133		458
Severance and related costs	0	$ 1,144	0	$ 2,668
COVID-19 related costs	2		94
Other	$ 131		$ 364