Discontinued Operations (Details Textual) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) from disposal of discontinued operations, net of tax			$ (17,367)	$ 0	$ 0
Environmental services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses	$ 100,000
Proceeds from sale of a business						$ 89,800
Gain (loss) from disposal of discontinued operations before income taxes		$ 34,000	(22,000)
Gain (loss) from disposal of discontinued operations, net of tax		22,100	(17,400)
Proceeds from divestiture of businesses, increase (decrease) sales price	(22,000)
Ecoserv [Member] | Environmental services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Escrow deposit	$ 8,000	$ 8,000	$ 8,000			8,000
Released 9 months from closing date | Ecoserv [Member] | Environmental services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Escrow deposit						4,000
Released 18 months from closing date | Ecoserv [Member] | Environmental services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Escrow deposit						$ 4,000