Revenues - Disaggreation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 335,030	$ 354,473	$ 659,891	$ 679,648
Fixed fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	219,481	240,605	428,401	459,629
Time and materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	93,383	91,947	193,063	174,833
Product sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	22,153	21,765	38,394	44,873
License fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13	156	33	313
United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	266,875	278,507	516,908	536,231
Canada
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	30,426	29,287	59,265	56,114
Europe
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,846	18,144	31,855	34,289
Other foreign
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	21,883	28,535	51,863	53,014
Infrastructure Solutions
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	160,732	148,311	295,159	277,179
Infrastructure Solutions | Fixed fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	149,532	137,951	274,794	256,948
Infrastructure Solutions | Time and materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Infrastructure Solutions | Product sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	11,187	10,204	20,332	19,918
Infrastructure Solutions | License fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13	156	33	313
Infrastructure Solutions | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	117,580	106,367	211,425	200,271
Infrastructure Solutions | Canada
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	15,607	13,417	27,876	24,233
Infrastructure Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	12,996	14,336	26,140	27,296
Infrastructure Solutions | Other foreign
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	14,549	14,191	29,718	25,379
Corrosion Protection
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	96,389	127,715	194,494	251,105
Corrosion Protection | Fixed fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	63,982	101,493	141,883	200,013
Corrosion Protection | Time and materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	21,441	14,661	34,549	26,137
Corrosion Protection | Product sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	10,966	11,561	18,062	24,955
Corrosion Protection | License fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Corrosion Protection | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	71,386	93,693	135,245	184,596
Corrosion Protection | Canada
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	14,819	15,870	31,389	31,881
Corrosion Protection | Europe
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,850	3,808	5,715	6,993
Corrosion Protection | Other foreign
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	7,334	14,344	22,145	27,635
Energy Services
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	77,909	78,447	170,238	151,364
Energy Services | Fixed fee
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	5,967	1,161	11,724	2,668
Energy Services | Time and materials
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	71,942	77,286	158,514	148,696
Energy Services | Product sales
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Energy Services | License fees
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Energy Services | United States
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	77,909	78,447	170,238	151,364
Energy Services | Canada
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Energy Services | Europe
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0	0	0
Energy Services | Other foreign
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 0	$ 0	$ 0	$ 0