Goodwill and Identified Intangible Assets - Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, gross	$ 393,615
Accumulated impairment losses	(94,996)
Goodwill, beginning balance	298,619
Additions to goodwill through acquisitions	3,377
Foreign currency translation	753
Goodwill, gross	397,745
Accumulated impairment losses	(94,996)
Goodwill, ending balance	302,749
Environmental Techniques
Goodwill [Roll Forward]
Additions to goodwill through acquisitions	3,400
Infrastructure Solutions
Goodwill [Roll Forward]
Goodwill, gross	239,494
Accumulated impairment losses	(16,069)
Goodwill, beginning balance	223,425
Additions to goodwill through acquisitions	3,377
Foreign currency translation	688
Goodwill, gross	243,559
Accumulated impairment losses	(16,069)
Goodwill, ending balance	227,490
Corrosion Protection
Goodwill [Roll Forward]
Goodwill, gross	73,875
Accumulated impairment losses	(45,400)
Goodwill, beginning balance	28,475
Additions to goodwill through acquisitions	0
Foreign currency translation	65
Goodwill, gross	73,940
Accumulated impairment losses	(45,400)
Goodwill, ending balance	28,540
Energy Services
Goodwill [Roll Forward]
Goodwill, gross	80,246
Accumulated impairment losses	(33,527)
Goodwill, beginning balance	46,719
Additions to goodwill through acquisitions	0
Foreign currency translation	0
Goodwill, gross	80,246
Accumulated impairment losses	(33,527)
Goodwill, ending balance	$ 46,719