Note 8 - Goodwill and Intangible Assets - Reconciliation Goodwill (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Goodwill, gross		$ 398,610	$ 402,408		$ 401,101
Accumulated impairment losses		(141,775)	(141,775)		(140,386)
Goodwill, Ending Balance		256,835	260,633		260,715
Acqusitions (1)	[1]		3,973
Impairments (2)		0	(1,389)	[1]	(45,390)
Foreign currency translation		426	(2,666)
Reclassification to assets held for sale (3)	[2]	(4,224)
Goodwill, net		256,835	260,633		260,715
Infrastructure Solutions [Member]
Goodwill, gross		240,160	244,521		246,486
Accumulated impairment losses		(62,848)	(62,848)		(61,459)
Goodwill, Ending Balance		177,312	181,673		185,027
Acqusitions (1)	[1]		0
Impairments (2)			(1,389)	[1]	(45,400)
Foreign currency translation		(137)	(1,965)
Reclassification to assets held for sale (3)	[2]	(4,224)
Goodwill, net		177,312	181,673		185,027
Corrosion Protection [Member]
Goodwill, gross		76,946	76,383		74,369
Accumulated impairment losses		(45,400)	(45,400)		(45,400)
Goodwill, Ending Balance		31,546	30,983		28,969
Acqusitions (1)	[1]		2,715
Impairments (2)	[1]		0
Foreign currency translation		563	(701)
Reclassification to assets held for sale (3)	[2]	0
Goodwill, net		31,546	30,983		28,969
Energy Services [Member]
Goodwill, gross		81,504	81,504		80,246
Accumulated impairment losses		(33,527)	(33,527)		(33,527)
Goodwill, Ending Balance		47,977	47,977		46,719
Acqusitions (1)	[1]		1,258
Impairments (2)	[1]		0
Foreign currency translation		0	0
Reclassification to assets held for sale (3)	[2]	0
Goodwill, net		$ 47,977	$ 47,977		$ 46,719

[1] During 2018, the Company recorded goodwill of $2.7 million and $1.3 million related to the acquisitions of Hebna and P2S, respectively (see Note 1).

[2] During 2019, the Company classified certain assets of its CIPP contracting operation in Europe as held for sale (see Note 6).