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Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Discontinued Operations (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale	$ 1,839		$ 1,839		$ 2,058
Loss from discontinued operations	(1,269)	$ (827)	(1,999)	$ (1,514)
Fuel Conversion Segment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Severance costs			582
Fuel Conversion Segment \| Period One
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Severance costs			402
Fuel Conversion Segment \| Period Two
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Severance costs			120
Fuel Conversion Segment \| Period Three
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Severance costs			60
Fuel Conversion Segment \| Unclassified Indefinite-lived Intangible Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale	1,354		1,354
Fuel Conversion Segment \| Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale	485		485
Fuel Conversion Segment \| Accrued Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued severance charges	$ 382		$ 382