DISCONTINUED OPERATIONS (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 05, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment of discontinued operations				$ 72,309	$ 0
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Current assets of discontinued operations	$ 83,331	$ 83,331		83,331			$ 88,472
Noncurrent assets of discontinued operations	106,510	106,510		106,510			181,036
Current liabilities of discontinued operations	57,316	57,316		57,316			47,499
Noncurrent liabilities of discontinued operations	8,236	8,236		8,236			13,000
Discontinued Operations, Held-for-sale | MEGTEC and Universal Businesses
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation, consideration transferred						$ 130,000
Goodwill impairment of discontinued operations	72,300
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenue		58,257	$ 43,598	116,439	86,630
Cost of operations		45,521	35,076	90,189	69,097
Selling, general and administrative		7,597	11,214	17,024	21,444
Goodwill impairment		72,309	0	72,309	0
Restructuring charge		0	151	0	151
Research and development		390	464	756	933
Loss on asset disposal		0	2	0	2
Operating loss		(67,560)	(3,309)	(63,839)	(4,997)
Net loss		(55,932)	$ (2,234)	(59,428)	(3,610)
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Cash and cash equivalents	10,437	10,437		10,437			12,950
Accounts receivable – trade, net	37,821	37,821		37,821			39,196
Accounts receivable – other	(1,430)	(1,430)		(1,430)			157
Contracts in progress	25,514	25,514		25,514			25,409
Inventories	8,540	8,540		8,540			9,245
Other current assets	2,449	2,449		2,449			1,515
Current assets of discontinued operations	83,331	83,331		83,331			88,472
Net property, plant and equipment	26,234	26,234		26,234			27,224
Goodwill	46,411	46,411		46,411			118,720
Deferred income taxes	1,462	1,462		1,462			359
Intangible assets	32,364	32,364		32,364			34,715
Other assets	39	39		39			18
Noncurrent assets of discontinued operations	106,510	106,510		106,510			181,036
Total assets of discontinued operations	189,841	189,841		189,841			269,508
Accounts payable	16,520	16,520		16,520			19,838
Accrued employee benefits	3,027	3,027		3,027			3,095
Advance billings on contracts	12,521	12,521		12,521			9,073
Accrued warranty expense	5,645	5,645		5,645			5,506
Other accrued liabilities	19,603	19,603		19,603			9,987
Current liabilities of discontinued operations	57,316	57,316		57,316			47,499
Pension and other accumulated postretirement benefit liabilities	6,231	6,231		6,231			6,388
Other noncurrent liabilities	2,005	2,005		2,005			6,612
Noncurrent liabilities of discontinued operations	8,236	8,236		8,236			13,000
Total liabilities of discontinued operations	$ 65,552	$ 65,552		65,552			$ 60,499
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Depreciation and amortization				3,036	5,307
Goodwill impairment				72,309	0
Provision for (benefit from) deferred income taxes				(815)	(275)
Purchase of property, plant equipment				77	486
Acquisition of Universal, net of cash acquired				$ 0	$ (52,547)