Goodwill and Identified Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, gross	$ 400,177		$ 400,177		$ 393,615
Accumulated impairment losses	(140,386)		(140,386)		(94,996)
Goodwill [Roll Forward]
Goodwill, beginning balance			298,619
Additions to goodwill through acquisitions			3,355
Goodwill impairment	(45,390)	$ 0	(45,390)	$ 0
Foreign currency translation			3,207
Goodwill, ending balance	259,791		259,791
Environmental Techniques
Goodwill [Roll Forward]
Additions to goodwill through acquisitions			3,400
Infrastructure Solutions
Goodwill [Line Items]
Goodwill, gross	245,491		245,491		239,494
Accumulated impairment losses	(61,459)		(61,459)		(16,069)
Goodwill [Roll Forward]
Goodwill, beginning balance			223,425
Additions to goodwill through acquisitions			3,355
Goodwill impairment	(45,400)		(45,390)
Foreign currency translation			2,642
Goodwill, ending balance	184,032		184,032
Corrosion Protection
Goodwill [Line Items]
Goodwill, gross	74,440		74,440		73,875
Accumulated impairment losses	(45,400)		(45,400)		(45,400)
Goodwill [Roll Forward]
Goodwill, beginning balance			28,475
Additions to goodwill through acquisitions			0
Goodwill impairment			0
Foreign currency translation			565
Goodwill, ending balance	29,040		29,040
Energy Services
Goodwill [Line Items]
Goodwill, gross	80,246		80,246		80,246
Accumulated impairment losses	(33,527)		(33,527)		$ (33,527)
Goodwill [Roll Forward]
Goodwill, beginning balance			46,719
Additions to goodwill through acquisitions			0
Goodwill impairment			0
Foreign currency translation			0
Goodwill, ending balance	46,719		46,719
Fyfe
Goodwill [Roll Forward]
Goodwill impairment	(45,400)
Goodwill, ending balance	$ 9,600		$ 9,600