WARRANTY EXPENSE (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement in Extended Product Warranty Accrual [Roll Forward]
Balance at beginning of period		$ 33,514	$ 36,520	$ 35,819
Additions		33,095	22,373	22,117
Expirations and other changes		(5,963)	(13,805)	(10,531)
Increases attributable to business combinations		0	0	918
Payments		(14,151)	(13,622)	(11,089)
Translation and other		(1,378)	2,048	(714)
Balance at end of period		45,117	33,514	36,520
Expected warranty costs		14,200
Babcock & Wilcox segment
Movement in Extended Product Warranty Accrual [Roll Forward]
Additions to warranty accrual	$ 4,300		7,900	2,100
Reduction of warranty expense		$ 4,500	$ 9,100	$ 4,400