Goodwill and Identified Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, gross	$ 401,404	$ 401,101
Accumulated impairment losses	(140,386)	(140,386)
Goodwill, beginning balance	260,715
Foreign currency translation	303
Goodwill, ending balance	261,018
Infrastructure Solutions
Goodwill [Roll Forward]
Goodwill, gross	247,058	246,486
Accumulated impairment losses	(61,459)	(61,459)
Goodwill, beginning balance	185,027
Foreign currency translation	572
Goodwill, ending balance	185,599
Corrosion Protection
Goodwill [Roll Forward]
Goodwill, gross	74,100	74,369
Accumulated impairment losses	(45,400)	(45,400)
Goodwill, beginning balance	28,969
Foreign currency translation	(269)
Goodwill, ending balance	28,700
Energy Services
Goodwill [Roll Forward]
Goodwill, gross	80,246	80,246
Accumulated impairment losses	(33,527)	$ (33,527)
Goodwill, beginning balance	46,719
Foreign currency translation	0
Goodwill, ending balance	$ 46,719