GEOGRAPHIC AND SEGMENT INFORMATION - NARRATIVE (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Segment Reporting [Abstract]
Number of operating segments (in segments) | segment				2
Concentration Risk [Line Items]
Income (loss) from continuing operations	$ (4,465)	$ (5,200)	$ (2,933)	$ (9,668)	$ (5,653)
Geographic concentration risk | Sales Revenue | International customers
Concentration Risk [Line Items]
Concentration receivable risk (as a percent)	30.90%		19.80%	30.20%	19.30%
Operating Segments | Advanced Energy
Concentration Risk [Line Items]
Income (loss) from continuing operations	$ (1,011)	(3,400)	$ (792)	$ (4,399)	$ (1,370)
Operating Segments | OEM
Concentration Risk [Line Items]
Income (loss) from continuing operations	136	800	302	921	708
Corporate & Other
Concentration Risk [Line Items]
Income (loss) from continuing operations	$ (3,590)	$ (2,600)	$ (2,443)	$ (6,190)	$ (4,991)