CHANGES IN BUSINESS (Details) - USD ($) $ in Thousands					3 Months Ended			12 Months Ended
	Mar. 21, 2018	Oct. 31, 2017	Oct. 11, 2017	Jan. 13, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Income (loss) before income taxes
Lloss from discontinued operations before income tax expense (benefit)					$ (1,708)		$ (4,244)
Income tax expense (benefit)					42		979
Income (loss) from discontinued operations					(1,750)		(5,223)
Loss from continuing operations before income tax expense					(1,953)		(13,463)
(Gain) loss on sale of business and net assets held for sale							239
Repayments of Long-term Debt							102,647
Disposed of by sale | Services | Hetsco Inc.
Income (loss) before income taxes
Write-down of assets held for sale									$ 8,300
Loss from continuing operations before income tax expense							489
(Gain) loss on sale of business and net assets held for sale							239
Proceeds from sale of business				$ 23,200
Escrow deposit				1,500
Repayment of debt				$ 20,200
Discontinued operations disposed of by sale | Mechanical Solutions
Income (loss) before income taxes
Revenue							16,678
Cost of revenue							13,530
(Gain) loss on sale of from disposal of discontinued operations					(24)	$ 6,300
Proceeds from sale of business			$ 43,000
Transition services period			9 months
Discontinued operations disposed of by sale | Mechanical Solutions | Maximum
Income (loss) before income taxes
Transition services expense					100
Discontinued operations disposed of by sale | Mechanical Solutions | Mexico
Income (loss) before income taxes
Proceeds from sale of property, plant and equipment		$ 3,600
Discontinued operations disposed of by sale | Mechanical Solutions | NETHERLANDS
Income (loss) before income taxes
Carrying value of property, plant and equipment						500		$ 500
Impairment charge						200
Fair value of property, plant and equipment						300		300
Proceeds from sale of property, plant and equipment	$ 300
Discontinued operations disposed of by sale | Mechanical Solutions | Centre Lane Term Facility
Income (loss) before income taxes
Repayments of Long-term Debt			$ 34,000
Discontinued operations disposed of by sale | Mechanical Solutions | Centre Lane Term Facility | Mexico
Income (loss) before income taxes
Repayments of Long-term Debt		$ 1,900
Discontinued operations, held-for-sale or disposed of by sale
Assets:
Accounts receivable					11,488	12,296		12,296
Inventories, net					160	178		178
Costs and estimated earnings in excess of billings					9,885	11,325		11,325
Other current assets					627	493		493
Property, plant and equipment, net					3,374	3,630		3,630
Total assets of discontinued operations					25,534	27,922		27,922
Liabilities:
Accounts payable					9,038	7,004		7,004
Accrued liabilities					1,073	1,191		1,191
Billings in excess of costs and estimated earnings					1,113	948		948
Accrued warranties					1,246	1,166		1,166
Other current liabilities					11,064	18,493		18,493
Current liabilities of discontinued operations					23,534	28,802		28,802
Liability for uncertain tax positions					3,193	3,110		3,110
Long-term liabilities of discontinued operations					3,193	3,110		3,110
Total liabilities of discontinued operations					26,727	31,912		31,912
Income (loss) before income taxes
Revenue					12,844		30,225
Cost of revenue					13,455		28,700
Selling and marketing expenses					(61)		1,269
General and administrative expenses					1,143		4,339
Other					39		161
Loss from discontinued operations before income tax expense (benefit)					(1,708)		(4,244)
Income tax expense (benefit)					42		979
Income (loss) from discontinued operations					(1,750)		(5,223)
Discontinued operations, held-for-sale | Electrical Solutions
Assets:
Goodwill and other intangible assets						$ 0		0
Income (loss) before income taxes
Write-down of assets held for sale								$ 9,700
Discontinued operations, held-for-sale | Electrical Solutions
Income (loss) before income taxes
Revenue					12,844		13,547
Cost of revenue					$ 13,455		$ 15,170