Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues	$ 333,998	$ 339,679	$ 335,030	$ 324,861	$ 337,499	$ 341,872	$ 354,473	$ 325,175	$ 1,333,568	$ 1,359,019	$ 1,221,920
Fixed fee
Disaggregation of Revenue [Line Items]
Revenues									868,993	932,406	840,263
Time and materials
Disaggregation of Revenue [Line Items]
Revenues									377,945	337,789	286,302
Product sales
Disaggregation of Revenue [Line Items]
Revenues									84,181	88,249	95,347
License fees
Disaggregation of Revenue [Line Items]
Revenues									2,449	575	8
United States
Disaggregation of Revenue [Line Items]
Revenues									966,291	1,028,313	924,580
Canada
Disaggregation of Revenue [Line Items]
Revenues									133,612	139,734	129,291
Europe
Disaggregation of Revenue [Line Items]
Revenues									66,794	71,839	60,238
Other foreign
Disaggregation of Revenue [Line Items]
Revenues									166,871	119,133	107,811
Infrastructure Solutions
Disaggregation of Revenue [Line Items]
Revenues									604,121	612,154	571,551
Infrastructure Solutions | Fixed fee
Disaggregation of Revenue [Line Items]
Revenues									556,642	569,701	524,311
Infrastructure Solutions | Time and materials
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Infrastructure Solutions | Product sales
Disaggregation of Revenue [Line Items]
Revenues									45,030	41,878	47,232
Infrastructure Solutions | License fees
Disaggregation of Revenue [Line Items]
Revenues									2,449	575	8
Infrastructure Solutions | United States
Disaggregation of Revenue [Line Items]
Revenues									430,187	437,944	425,990
Infrastructure Solutions | Canada
Disaggregation of Revenue [Line Items]
Revenues									62,292	60,675	47,587
Infrastructure Solutions | Europe
Disaggregation of Revenue [Line Items]
Revenues									54,567	58,520	45,046
Infrastructure Solutions | Other foreign
Disaggregation of Revenue [Line Items]
Revenues									57,075	55,015	52,928
Corrosion Protection
Disaggregation of Revenue [Line Items]
Revenues									393,740	456,139	401,469
Corrosion Protection | Fixed fee
Disaggregation of Revenue [Line Items]
Revenues									296,217	353,480	301,114
Corrosion Protection | Time and materials
Disaggregation of Revenue [Line Items]
Revenues									58,372	56,288	52,240
Corrosion Protection | Product sales
Disaggregation of Revenue [Line Items]
Revenues									39,151	46,371	48,115
Corrosion Protection | License fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Corrosion Protection | United States
Disaggregation of Revenue [Line Items]
Revenues									200,397	299,643	249,690
Corrosion Protection | Canada
Disaggregation of Revenue [Line Items]
Revenues									71,320	79,059	81,704
Corrosion Protection | Europe
Disaggregation of Revenue [Line Items]
Revenues									12,227	13,319	15,192
Corrosion Protection | Other foreign
Disaggregation of Revenue [Line Items]
Revenues									109,796	64,118	54,883
Energy Services
Disaggregation of Revenue [Line Items]
Revenues									335,707	290,726	248,900
Energy Services | Fixed fee
Disaggregation of Revenue [Line Items]
Revenues									16,134	9,225	14,838
Energy Services | Time and materials
Disaggregation of Revenue [Line Items]
Revenues									319,573	281,501	234,062
Energy Services | Product sales
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Energy Services | License fees
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Energy Services | United States
Disaggregation of Revenue [Line Items]
Revenues									335,707	290,726	248,900
Energy Services | Canada
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Energy Services | Europe
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Energy Services | Other foreign
Disaggregation of Revenue [Line Items]
Revenues									$ 0	$ 0	$ 0