Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, gross	$ 402,271	$ 401,101
Accumulated impairment losses	(140,386)	(140,386)
Goodwill, beginning balance	260,715
Acquisitions	2,629
Foreign currency translation	(1,459)
Goodwill, ending balance	261,885
Infrastructure Solutions
Goodwill [Roll Forward]
Goodwill, gross	245,420	246,486
Accumulated impairment losses	(61,459)	(61,459)
Goodwill, beginning balance	185,027
Acquisitions	0
Foreign currency translation	(1,066)
Goodwill, ending balance	183,961
Corrosion Protection
Goodwill [Roll Forward]
Goodwill, gross	76,605	74,369
Accumulated impairment losses	(45,400)	(45,400)
Goodwill, beginning balance	28,969
Acquisitions	2,629
Foreign currency translation	(393)
Goodwill, ending balance	31,205
Energy Services
Goodwill [Roll Forward]
Goodwill, gross	80,246	80,246
Accumulated impairment losses	(33,527)	$ (33,527)
Goodwill, beginning balance	46,719
Acquisitions	0
Foreign currency translation	0
Goodwill, ending balance	46,719
Hebna | Corrosion Protection
Goodwill [Roll Forward]
Acquisitions	$ 2,600