Note 7 - Goodwill and Intangible Assets - Reconciliation Goodwill (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020		Sep. 30, 2019	Dec. 31, 2019
Goodwill, gross		$ 398,803			$ 398,803			$ 398,610
Accumulated impairment losses		(182,463)			(182,463)			(141,775)
Goodwill, Ending Balance		216,340			216,340			256,835
Impairments (1)(2)		(39,430)		$ 0	(40,688)	[1],[2]	$ 0
Foreign currency translation					193
Infrastructure Solutions [Member]
Goodwill, gross		240,594			240,594			240,160
Accumulated impairment losses		(62,848)			(62,848)			(62,848)
Goodwill, Ending Balance		177,746			177,746			177,312
Impairments (1)(2)	[1],[2]				0
Foreign currency translation					434
Corrosion Protection [Member]
Goodwill, gross		76,705			76,705			76,946
Accumulated impairment losses		(45,400)			(45,400)			(45,400)
Goodwill, Ending Balance		31,305			31,305			31,546
Impairments (1)(2)	[1],[2]				0
Foreign currency translation					(241)
Energy Services [Member]
Goodwill, gross		81,504			81,504			81,504
Accumulated impairment losses		(74,215)			(74,215)			(33,527)
Goodwill, Ending Balance		7,289			7,289			$ 47,977
Impairments (1)(2)		$ (39,400)	$ (1,300)		(40,688)	[1],[2]
Foreign currency translation					$ 0

[1] During the second quarter of 2020, the Company recorded a $1.3 million goodwill impairment related to restructuring activities within Energy Services (see Note 4).

[2] During the third quarter of 2020, the Company recorded a $39.4 million goodwill impairment within Energy Services (see Note 2).