Accounting Policies - Classification of Current Assets and Current Liabilities and Retainage (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Line Items]
Billings in excess of costs and estimated earnings	$ 51,597	$ 62,698
Increase (decrease) in billings in excess of costs and estimated earnings	(5,924)	(27,761)	$ 45,700
Prepaid expenses and other current assets	35,282	51,832
Increase (decrease) in prepaid expenses and other assets	$ (8,732)	(16,759)	$ 28,895
Retainage collection period upon completion of contract	1 year
Contract receivable retainage due after 12 months percent	10.00%
Bayou Coating
Accounting Policies [Line Items]
Billings in excess of costs and estimated earnings	$ 51,600	$ 62,700
Increase (decrease) in billings in excess of costs and estimated earnings	(11,100)
Increase (decrease) in prepaid expenses and other assets	$ (16,600)
Minimum
Accounting Policies [Line Items]
Collection period for municipalities	60 days
Retainage, percent of contract value withheld	5.00%
Collection period for other than municipalities	30 days
Minimum | Bayou Coating
Accounting Policies [Line Items]
Construction period (less than 1 month)	1 month
Maximum
Accounting Policies [Line Items]
Collection period for municipalities	90 days
Retainage, percent of contract value withheld	15.00%
Collection period for other than municipalities	45 days
Maximum | Bayou Coating
Accounting Policies [Line Items]
Construction period (less than 1 month)	24 months